The boring answer:
If you are omnipotent, by definition, you can be anything and exist wherever/whenever/however you want.
On the more longwinded side:
The question doesn't make much sense. When using any of the "omni-"s, you kind of have to accept that ordinary logic doesn't apply. Omnipotence especially, almost requires that it doesn't adhere to any logical rules or you run into problems like "Can God create a boulder he can't lift?"
An omnipotent beeing, by it's nature, can have any nature it desires, at the same time, or none at all. Concepts like time, position, existence, or causation only affect it in so far as it wants it to. It is defined by what it wants, not what it is (and even that it can change without stopping being omnipotent).
Or you can go the other way and simply say, as for as humans can comprehend it, there can be no true omnipotence, because there can be no paradoxes.
From a practical point of view
We have no idea of the mechanics of free will, nor of omnipotence, nor of omniscience, and only a limited understanding of time/space, thus we can make no assumptions about how they interact or what their requirements are.