Krsna as His original eternal childhood infinite Form NEVER leaves Vṛndāvana.

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, 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 however, there is no difference in Their potency."(SB, Canto 3 Ch 1 Text 34)

Krsna is likened to the original candle that lights all other candles of the same luminosity.

Only Kṛṣṇa has all of His 64 qualities in full all the time, unlike all the other variety of living entities like-

1 - Visnu-tattva (Balarama, Visnu, Narayana, Maha-Visnu, Garbhodakashayi Visnu, Paramatma) exhibits 60 of 64 or 93.75% 

2 - Visnu-"sakti"-tattva (Radharani and Her eternal associates or internal potency exhibits 60 of the 64 also 93.75% 

3 - Siva-tattva (Lord Siva) exhibits 55 of the 64 or 85.938%

4 - The Jiva-tattvas, (marginal living entities or jiva-souls) exhibits 50 of the 64 which is 78.125%. 

Krsna, as His original infinite Form, has 64 qualities of which 4 of those are unique to only Kṛṣṇa, only partially exhibited by some Visnu-tattva expansions.

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, Ch 10 Text 37)

Kṛṣṇa’s first expansion is Balarama, from Balarama ALL the other Visnu-tattva expansions who each have their own unique name, originate.

When the "original" Krsna wants to enter the material creation to perform His pastimes in the Vrindavana, a facsimile of the spiritual world, it is His Visnu-tattva expansion, who is an expansion of Balarāma, who plays the part of Kṛṣṇa.  

In other words, it is a Visnu-tattva tattva expansion of Balarāma who performs those "Kṛṣṇa pastimes" or lilas.

In other words, because the original infinite Kṛṣṇa NEVER leaves Vṛndāvana, His Visnu-tattva expansion (coming from Balarāma), plays the part of the original Kṛṣṇa in the material creation and includes killing demons there.

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

Visnu-tattva is an expansion of Balarāma, it is the Visnu-tattva expansion who plays the part of the two-armed Krsna outside of the spiritual world, who enters the material creation and kills many demons.

Such killing of demons do not happen in the original Vṛndāvana in the spiritual worlds, it only happens in the "facsimile of the original Vṛndāvana" that is in the material creation that is almost non different than the original.

All Visnu-tattva/Narayana expansion do not have those 4 extra qualities Krsna has always. 

Therefore, Krsna is always the Supreme Personality of Godhead and cause of all causes and expands Himself into innumerable categories of living entities - from Visnu-tattva, to Visnu-sakti-tattva, to Siva-tattva, to jiva-tattva (jiva-souls)

Of all the living entities, the ones who are almost equal to Krsna are called Visnu-tattva (Balarama etc) and Visnu-"sakti"-tattva (Radharani and Her eternal unlimited associates)

While other living entities like the marginal living entities (jiva-souls), are separated and therefore more independent from Krsna than His Visnu-tattva and Visnu-"sakti"-tattva  expansions.

The jiva-souls have their own unique independent personality, character and identity separate from Krsna's Personality. 

The individual jiva-souls each have their own unique ability of independent self expression, this allows the  to voluntarily contribute in a unique creative manner serving who thinks for themselves and never told how and what to think or do.

The jiva-souls therefore, have their own unique "sense of being an independent PERSON," who can express themselves in the way they choose to voluntarily serve Radha and Krsna, or even reject Them.

In the spiritual world Maya or the material energy, does not exist, so the individual jiva-souls can NEVER be tempted by Maya or material energy on the Vaikuntha planets, or in Krsna's central Abode of Goloka Vrindavana.  

However, what does eternally exist in the spiritual world is free will or v self-expression which is the only cause of fall down from the Vaikuntha planets and Goloka-Vrindavana.

As explained above, Lord Siva (Siva-tattva), is neither Visnu-tattva or jiva-tattva (jiva-soul) but is in a league of his own with his followers.

All are Krsna's expansions, each have a portion of His 64 qualities however, only Kṛṣṇa has all 64 qualities in full all the time.

As a reminder-

Visnu-tattva and Visnu-"sakti"-tattva expansions have 60 of Krsna's 64 qualities which is 93.75%. 

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

Jiva-tattvas (jiva-souls) expansions have 50 of Krsna's 64 qualities which is 78.125%.

Being all-powerful and the cause of all causes, Krsna can expand Himself into unlimited Forms with the same power and characteristics He possesses, without diminishing Himself in anyway.×<×.