Did Adam have a belly button ?

God does not need anything or anyone to create. He is Almighty God he created everything in the beginning by the word of his mouth. Jesus is the Fathers Word made flesh. He was there in eternity past and he will always be into eternity future.

The creator doesn't need anyone to do anything. He just says be and it is. He can create me and you and this universe and he can create Adam without parents and Jesus without father.

It was to validate prophecy and that He was the true messiah. We always asks for signs, God set up the signs, prophesied them, and made them come to pass.

Remember that God does not need anything. But rather that God chose to be born through the Virgin Mary in humility, to ultimately conquer death and redeem mankind. There was no impregnation for the creation of Adam, for Adam was formed from the dust and was the first human, created and not born. Hope this helps. I guarantee someone else could explain it better, but this is just a simple frame of reference.