well, under my favorite theory, all attempts to kill your father must have failed cause you ARE alive. heh
Under secular theory, I don't believe time travel is possible - nor are there multiple dimensions.
However, under theistic theory, it may be possible that God can revert the universe to an earlier state - or a future state. Since he knews the past and the future and is all-powerful - than sure, he can cause time travel if he wants. It's like taking a tape recorder and pushing rewind and fast forward. There's nothing stopping him from creating multiple dimensions too - who knows, maybe he already has. Maybe angel's can flit between our reality and some other parallel universe that exists right here and now but we cannot see unless God wills it.