you can not jump between universes because a universe is by definition not connected to any other universe. uni means one. we can not escape our universe for a number of reasons, but a big one is the period of inflation following the big bang when our universe expanded at a rate exponentially faster than the speed of light which makes it impossible for us to ever travel to its edge, let alone beyond it. but even if you could escape our universe to jump into another, why would that have anything to do with time travel? you are talking two totally different things. but lets say you also have a time machine that you brought, you would quickly discover another problem, there is an infinite number of universes in the multiverse so unless you know which one you are going to and when it fractured from the one you are in, how would you ever know where and when to go? there is an infinite number so how do you even start to map that out? if you traveled to a universe that split back at the beginning of time, there would be no guarantee that earth would even exist. in fact, the multiverse would be full of empty universes where gravity was not strong enough to pull the first hydrogen atoms together to form the first stars, or inflation happened at a faster rate and the first stars were not able to coalesce, or the matter / anti-matter balance was different so there is no matter at all, or only anti-matter remains. and one last thing to consider, time is not a constant, it is speed up and slowed down by gravity amongst other things and in fact, time may not exist at all, it may simply be a byproduct of the motion that our universe is in with the motion creating the illusion of time to an observer.