Yeah it would be fun and go back to mess with all the weird things about in whatever time, but what if it changed everything that was here and now to something else? What if it changed into the u.s being ruled by britian still, cars never came about, or Electricity was never converted? everything could be undone by simply messing with something or someone from another time. If their were parrall rifts around that could change alot of what people see now, because it could all be backwards, or forwards. It could make you wish we were more advanced, or primitive, theres plenty of possbilities of what the world could have been like long ago, now or in the future. time rifts could show many people to appreciate what we have.
the whole thing of being in a time with yourself? i dont think thats possible since that could change the course of your lifeline, and it cannot sustain two of the same. It would delete one from that course, and let the other continue on. If your past is gone, will you still be alive? or would you die as well? Now if your past continues on does is make the choice to make that same decision to repeat that corse, or choose a different path?
but no one knows since its never happened so its better to expect anything to happen when it does or even comes about. Its to complex and complicated, scientics are more invovled with the creation of things, and bio chemicals than time travel at the moment.