ok, don't get me started on the time theories.
At the last count there were five scientifically accepted hypothesis. (correct me if im wrong)
But only two types could support your theories on Mikuru,
#1. Multi-universe paradox branching.
I.e. Everytime you change the course of the establish time of event, your alteration creates a parallel alternative universe to accommodate your change, thus you will never ever be able to return to your future original distination.
#2. the other is that time is infinity mallable, but your personal self will continue to exist, dispite the change of time events thus you will exist in this new timeline yet still retain perfect memory of your original timeline history.
at this moment im not so sure which one the author is using, but it's a good chance its not going to be one of those two types that will allow your speculation.
ah, but then again, Hollywood always did like theory #2
ahh dammit. I give up on all this heavy topics, its not something i should be doing at 4am. >.<