An Aura being put onto the battlefield this way can’t enchant anything else that is being put onto the battlefield at the same time.

Any abilities that trigger as the permanents enter the battlefield this way won't be put onto the stack until after Genesis Ultimatum has finished resolving and is in exile.

If an Aura is put onto the battlefield without being cast, the Aura's controller-to-be chooses what it will enchant as it enters the battlefield. An Aura put onto the battlefield this way doesn't target anything (so it could be attached to an opponent's permanent with hexproof, for example), but the Aura's enchant ability restricts what it can be attached to. If the Aura can't legally be attached to anything, it remains in its current zone.

An Aura being put onto the battlefield this way can't enchant anything else that is being put onto the battlefield at the same time.

You can choose to not put a permanent card onto the battlefield this way. You'll put it into your hand without revealing it and without saying whether it was a permanent card.

You can choose to not put any permanent cards onto the battlefield this way. You’ll put them into your hand without revealing them and without saying whether any of them were permanent cards.

Any abilities that trigger as the permanents enter the battlefield this way won’t be put onto the stack until after Genesis Ultimatum has finished resolving and is in exile.

If an Aura is put onto the battlefield without being cast, the Aura’s controller-to-be chooses what it will enchant as it enters the battlefield. An Aura put onto the battlefield this way doesn’t target anything (so it could be attached to an opponent’s permanent with hexproof, for example), but the Aura’s enchant ability restricts what it can be attached to. If the Aura can’t legally be attached to anything, you can’t choose to put it onto the battlefield; in this case, it would be put into your hand along with any other cards that weren’t put onto the battlefield this way.