I think that Gabriel told Mary that her prospective baby was boy, so that fact was known in advance and presumably a deliberate act of God, if indeed we believe it!!
I would love to believe in the after life, but somehow if I'm totally honest I have grave doubts, it's too complicated for a mere human to visualise and from the outside looking in completely impossible.
As to why we are here - well there's a question? Goodness only knows, some people it seems were put on this earth to do good, countermanded by those it would appear who were created for the exact opposite. Most of us muddle by and there appears to be no particular reason for our existence. Why do some live into old age and others die as babies. Is the earth the only inhabited planet? So many questions, most of them unanswerable. I don't know why we're here, who or what created animal life or what will be the end of it all.