If you somehow control more than one Oath of Teferi, you won’t be able to activate abilities of planeswalkers you control more than twice in one turn.

If a token is exiled this way, it ceases to exist and won’t return to the battlefield.

For Oath of Teferi’s second ability, you may activate the same ability of a planeswalker twice, or you may activate two different abilities of that planeswalker.

If the exiled card is an Aura, that card’s owner chooses what it will enchant as it returns to 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 exiled.

The exiled card will return to the battlefield at the beginning of the next end step even if Oath of Teferi is no longer on the battlefield at that time.