Krsna the Supreme Personality of Godhead and cause of all causes is likened to the original candle that lights all other candles of the same luminosity.

Krsna has all of His 64 qualities in full, unlike all His other expansions who can only partially exhibit such attributes. 

Therefore, Krsna has 64 qualities of which 4 are unique to only Kṛṣṇa that not even Visnu/Narayana fully exhibit. 

Krsna as His original childhood form never leaves Vṛndāvana therefore all His pastimes in the material world are performed by His Visnu-tattva expansion who plays the role of Krsna.

Srila Prabhupada - "Kṛṣṇa as His original childhood form NEVER leaves Vṛndāvana, all the forms of Kṛṣṇa that appear elsewhere are His Viṣṇu-tattva expansions." (BG As It Is Ch 10 text 37)

Srila Prabhupada - "The original Lord Kṛṣṇa never leaves Goloka Vṛndāvana. All the plenary expansions are one and the same Viṣṇu-tattva, and there is no difference in Their potency." (SB, Canto 3 Ch 1 Text 34)

Srila Prabhupada - "Kṛṣṇa is the original Supreme Personality of Godhead, and Baladeva (Balarama) is Kṛṣṇa's immediate expansion. Because Kṛṣṇa NEVER leaves Vṛndāvana, all the forms of Kṛṣṇa that appear elsewhere are His expansions." (BG, As It Is Ch 10 Text 37)

Kṛṣṇa’s first expansion is Balarama and from Him ALL Visnu-tattva expansions originate. 

Krsna also wanted to experience the loving affection and exchanges with a women, so to experience this, He divided Himself into two and became Radharani and Krsna.

And when Radharani and Krsna become one again in the same spiritual Body, that is Lord Caitanya Mahaprabhu.

When the "original" Krsna wants to enter the material creation to perform His pastimes in the "Vrindavana facsimile" of the spiritual world, His Visnu-tattva expansion performs those pastimes of Krsna.

In other words, because the original Kṛṣṇa NEVER leaves Vṛndāvana, His Visnu-tattva expansion plays the part of the original Kṛṣṇa in the material creation, that includes killing demons there. In the spiritual world Kṛṣṇa does not kill demons because they do not exist there, only in the material world does Krsna kill demons.

When Kṛṣṇa wants to enter the Vaikuntha planets, and the material creation, He first expands Himself as Balarāma (His older brother in Vṛndāvana) and from Balarama, all Visnu-tattva expansions manifest.

This includes a Visnu-tattva expansion of Balarāma who plays the part of the two-armed Krsna who enters the material creation and even kills many demons.

As said above, the killing of demons do not happen in the original Vṛndāvana in the spiritual world, it only happens in the "facsimile of the original Vṛndāvana" in the material creation.

Krsna is always the Supreme Personality of Godhead and cause of all causes and expands into innumerable categories of living entities. 

Of those living entities, the ones who are almost equal to Krsna are called Visnu-tattva.

Others living entities like jiva-tattva (jiva-souls) are more independent from Krsna who each have their own unique personality separate from Krsna's Personality. 

Srila Prabhupada - "The "immediate" expansions of the Lord are called svāṁśa or personal direct expansions (Visnu-tattva who are Krsna playing another role in His own pastimes) The "separated" expansions of the Lord are called vibhinnāṁśa - (jiva-tattva) or independent jiva-souls like us." (BG, Ch 10 Text 37, Purport)

Another living entity, Siva-tattva, is neither Visnu-tattva or jiva-tattva but is in a league of his own. All are Krsna's expansions each having a portion of Krsna's 64 qualities. However, only Kṛṣṇa has all 64 qualities in full all the time.

Visnu-tattva expansions have 60 of Krsna's 64 qualities which is 93.75% of Krsna's 100% attributes. 

Siva-tattva expansion has 55 of Krsna's 64 qualities which is 85.938% of Krsna's 100% attributes.

Jiva-tattva (jiva-soul) expansion has 50 of Krsna's 64 qualities which is 78.125% of Krsna's 100% attributes.

Being all-powerful Krsna can expand Himself into forms with the same power and characteristics He possesses, without diminishing Himself in anyway.

Srimad Bhagavatam - "All of the incarnations are either plenary portions or portions of the plenary portions of the Lord, but Lord Śrī Kṛṣṇa is the original Personality of Godhead. All of them appear on planets whenever there is a disturbance created by the atheists. The Lord incarnates to protect the theists." (SB, Canto I Ch 3 text 28)

Srila Prabhupada - "Learned scholars in transcendental subjects have carefully analyzed the summum bonum Kṛṣṇa to have sixty-four principal attributes. All the expansions or categories of the Lord possess only some percentages of these attributes. But Śrī Kṛṣṇa is the possessor of the attributes cent percent. 

And His personal expansions such as svayam-prakāśa, tad-ekātmā up to the categories of the avatāras who are all viṣṇu-tattva, possess up to ninety-three percent of these transcendental attributes. Lord Śiva, who is neither avatāra nor āveśa nor in between them, possesses almost eighty-four percent of the attributes.

But the jīvas, or the individual living beings in different statuses of life, possess up to the limit of seventy-eight percent of the aattributes. ln the conditioned state of material existence, the living being possesses these attributes in very minute quantity, varying in terms of the pious life of the living being. 

The most perfect of living beings is Brahmā, the supreme administrator of one universe. He possesses seventy-eight percent of the attributes in full.  All other demigods have the same attributes in less quantity, whereas human beings possess the attributes in very minute quantity. The standard of perfection for a human being is to develop the attributes up to seventy-eight percent in full. The living being can never possess attributes like Śiva, Viṣṇu or Lord Kṛṣṇa. 

A living being can become godly by developing the seventy-eight-percent transcendental attributes in fullness, but he can never become a God like Śiva, Viṣṇu or Kṛṣṇa. He can become a Brahmā in due course. The godly living beings who are all residents of the planets in the spiritual sky are eternal associates of God in different spiritual planets called Hari-dhāma and Maheśa-dhāma. 

The abode of Lord Kṛṣṇa above all spiritual planets is called Kṛṣṇaloka or Goloka Vṛndāvana, and the perfected living being, by developing seventy-eight percent of the above attributes in fullness, can enter the planet of Kṛṣṇaloka after leaving the present material body." (SB, Canto I Ch 3 text 28 Purport)

As said above, Krsna always has four more qualities than His Visnu/Narayana (Visnu-tattva) forms of Godhead have. His Visnu-tattva expansions can partially exhibit them but generally have only 60 of Krsna's 64 qualities.

Those four unique qualities Krsna ALWAYS has in full are- 

(1) He is the performer of wonderful varieties of pastimes (especially His childhood pastimes), 

(2) He is surrounded by devotees endowed with wonderful love of Godhead,

(3) He can attract all living entities all over the universes by playing on His flute, 

(4) He has a wonderful excellence of beauty which cannot be rivaled anywhere in the creation.

Srila Rupa Gosvami, after consulting various scriptures, gives us the 64 qualities of the Krsna as follows- 

(1) beautiful features of the entire body,

(2) marked with all auspicious characteristics; 

(3) extremely pleasing,

(4) effulgent; 

(5) strong; 

(6) ever-youthful; 

(7) wonderful linguist; 

(8) truthful; 

(9) talks pleasingly; 

(10) fluent; 

(11) highly learned, 

(12) highly intelligent; 

(13) a genius; 

(14) artistic; 

(15) extremely clever; 

(16) expert; 

(17) grateful; 

(18) firmly determined; 

(19) an expert judge of time and circumstances; 

(20) sees and speaks on the authority of Vedas, or scriptures; 

(21) pure; 

(22) self-controlled; 

(23) steadfast; 

(24) forbearing; 

(25) forgiving; 

(26) grave; 

(27) self-satisfied; 

(28) possessing equilibrium; 

(29) magnanimous; 

(30) religious,

(3l) heroic; 

(32) compassionate, 

(33) respectful,

(34) gentle; 

(35) liberal; 

(36) shy; 

(37) the protector of surrendered souls; 

(38) happy; 

(39) the well-wisher of devotees; 

(40) controlled by love; 

(4l) all-auspicious; 

(42) most powerful,

(43) all-famous, 

(44) popular, 

(45) partial to devotees, 

(46) very attractive to all women; 

(47) all-worshipable; 

(48) all-opulent; 

(49) all-honorable; 

(50) the supreme controller.

(51) changeless; 

(52) all-cognizant; 

(53) ever-fresh; 

(54) sac-cid-ananda-vigraha (as an eternal spiritual bodily form),

(55) possessing all mystic perfections,

(56) He has inconceivable potency,

(57) Uncountable universes generate from His body,

(58) He is the original source of all incarnations, 

(59) He is the giver of salvation to the enemies whom He kills, 

(60) He is the attractor of liberated souls. 

All these transcendental qualities are manifest wonderfully in the personal feature of Lord Krsna.

Besides these sixty transcendental qualities, Krsna has four more, which are not manifest even in the Narayana (Visnu) form of Godhead, what to speak of the demigods or living entities.

They are as follows- 

(61) He is the performer of wonderful varieties of pastimes (especially His childhood pastimes), 

(62) He is surrounded by devotees endowed with wonderful love of Godhead,

(63) He can attract all living entities all over the universes by playing on His flute, 

(64) He has a wonderful excellence of beauty which cannot be rivaled anywhere in the creation.

Srila Rupa Gosvami has attempted to give evidences from various scriptures about all sixty-four qualities present in the person of the Supreme Lord.” (From "Nectar of Devotion," Ch 21)

In the First Canto of Srimad-Bhagavatam in connection with a conversation between the deity of the earth and the King of religion, Yamaraja, it is said therein-

“Persons who are desirous of becoming great personalities must be decorated with the following 39 qualities"-

1 - truthfulness, 

2 - cleanliness, 

3 - mercy, 

4 - perseverance, 

5 - renunciation, 

6 - peacefulness, 

7 - simplicity, 

8 - control of the senses, 

9 - equilibrium of the mind, 

10 - austerity, 

11 - equality, 

12 - forbearance, 

13 - placidity, 

14 - learning, 

15 - knowledge, 

16 - detachment, 

17 - opulence, 

18 - chivalry, 

19 - influence, 

20 - strength, 

21 - memory, 

22 - independence, 

23 - tactfulness, 

24 - luster, 

25 - patience, 

26 - kindheartedness, 

27 - ingenuity, 

28 - gentility, 

29 - mannerliness, 

30 - determination, 

31 - perfection in all, 

32 - knowledge, 

33 - proper execution,

34 - possession of all objects of enjoyment, 

35 - gravity, 

36 - steadiness, 

37 - faithfulness, 

38 - fame, 

39 - respectfulness and lack of false egotism.

Persons who are desiring to become great souls cannot be without any of the above qualities, so we can know for certain that these qualities are found in Lord Krsna, the supreme soul.

Lord Krsna and Lord Caitanya both come ONLY "once" to this universe every 8 billion 640 million human years.

Lord Caitanya Mahaprabhu is the Golden Avatara for this degraded age of Kali-yuga, however, Lord Caitanya does NOT appear in every Kali-yuga, He only appears in ONE Kali-yuga out of every thousand, or once in a day of Brahma. (every 8 billion 640 million human years)

Just like Lord Krsna in His original form, also only appears in ONE Dvāpara-yuga out of every thousand.

Lord Krsna appears in the Dvāpara-yuga just before the Kali-yuga Lord Caitanya appears in. This means both Lord Krsna and Lord Caitanya come ONLY "once" every 8 billion 640 million human years, which is a "day/night" 24 hour period of Lord Brahma time.

Srila Prabhupada – "Lord Kṛṣṇa and Lord Caitanya appear "once" in each day of Brahmā." (CC, Adi 3.10 Text 10 Purport)

Srila Prabhupada –"At the end of the Dvāpara-yuga of the twenty-eighth Maha-yuga (during the 7th Manu known as Vaivasvata Manu), Lord Kṛṣṇa appears on earth with the full paraphernalia of His eternal Vraja-dhāma." (CC, Adi 3.10 Text 10)

Therefore during the 28th Maha-yuga of the Vaivasvata Manu (the 7th Manu of 14), Lord Kṛṣṇa first appears at the close of the Dvāpara-yuga and then Lord Caitanya appears in the Kali-yuga of the same Maha yuga.

Lord Kṛṣṇa and Lord Caitanya appear ONLY "once" in a day of Brahmā during the 7th Manu out of the fourteen, called Vaivasvata Manu.

First Lord Kṛṣṇa appears at the close of the Dvāpara-yuga of the twenty-eighth Maha-yuga in the Vaivasvata Manu (the 7th Manu), and then Lord Caitanya appears in the Kali-yuga of the same Maha yuga in Vaivasvata Manu.

Devotee - "Śrīla Prabhupāda, does Lord Caitanya Mahāprabhu also appear every day of Brahma?"

Srila Prabhupāda - "Yes, following Kṛṣṇa. Kṛṣṇa comes in the Dvāpara-yuga. There are four periods of each yuga: Satva, Tretā, Dvāpara, Kali. So Kṛṣṇa comes at the end of Dvāpara-yuga, and Caitanya Mahāprabhu comes in the Kali-yuga." (Lecture SB, Canto 6 Ch 1 Text 3, Melb, Australia May 22, 1975)

Our Kali-yuga is very rare because of Lord Caitanya Mahaprabhu's appearance. Also Lord Krsna, as His original form, appears only in the Dvāpara-yuga just before the Kali-yuga Lord Caitanya Mahaprabhu appears in.

Therefore Lord Krsna also does not appear as His original Vrindavana form in every Dvāpara-yuga, He only comes to ONE Dvāpara-yuga out of every thousand as said above.

Both Lord Krsna and Lord Caitanya Mahaprabhu only come "ONCE" in every "day/night" of Lord Brahma (between sun-rise and sun-set) when all the 1000 Maha-yugas are active. There are no Maha-yugas during Brahma's night while he sleeps (from sun-set to sun-rise).

In our current kalpa (day-time hours of Brahma from Sun-rise to Sun-set) there are fourteen Manus, we are in the 7th Manu known as Vaivasvata Manu. During Brahma's night-time period from Sun-set to Sun-rise, there are "no Maha-yugas."

Therefore during this inactive night-time period of Brahma (also called a Kalpa) he sleeps while a parcel  annihilation goes on until the next Sun-rise begins, starting  with the first Maha-yuga out of one thousand that all happen only during Brahma's day-time.   

Lord Brahma's 100 year life span in human years is 311 trillion and 40 billion years.^^