OK... let me start by stating the obvious: I don't know certain answers to any of this, and I'm not sure I even believe what I'm about to say, just playing with ideas here... But I'm about to throw out a totally wacky idea that goes along with the flatland analogy Andrew mentioned earlier. It's been my thought for a while that some Biblical paradoxes (mainly free will vs. predestination) can be resolved by viewing things from both a linear/temporal perspective, and an eternal non-temporal perspective. God seems to exist outside of time, as He knows the end from the beginning. We see things like prophecies fulfilled, and prayers whose answers are set in motion before they are prayed. The analogy I like to use when explaining it to kids is that if you draw time as a line on a sheet of paper, God is nowhere on the line, or even on the paper; He is in the room that the paper is in.
So... imagine if, from a linear perspective, Jesus first came into being at His virgin conception (no human father, thus not under sin), was filled with Spirit, grew to a man, lived in perfect submission to His Heavenly Father, died and was raised, and ascended to Heaven. Then, He is glorified into eternity, in essence stepping out of time (lifting out of the paper, as it were). At this point, because He is now outside of time, like the Father, He exists at all points throughout time, including in the eternal past, where He is pre-existent, and at the Creation of the world, where He then creates the world that would/did give Him birth.
I'm not really sure I personally like this idea, or that I believe it. Like I said, I'm just playing with different ideas, to see whether there's a way both views can be true. Do with that what you will.
To quote Captain Janeway, "Temporal mechanics give me a headache."