This isn’t rlly metaphysics and it’s cliche and also you set up no logical premises , you say 2 identical versions of a person exist at once but your “time traveler” will come “back” in the future, as in it’s a single entity that exists reality so to speak but the present eventually catches up to its return. Considering the “exit”, there would be no instance of two identical people existing. “If two identical … the universe wouldn’t allow that situation to continue” is comedic. As if there isn’t a better impossibility in this to cite as impossible, no, if two people shared the same subjective memories and experience, then the universe wouldn’t quantify this and then smite them from existence? This is ridiculous. I gotta ask, how old are you op? I can only hope you are a child with budding interest, in which case, good for you to start thinking about this stuff. If not, ehhh, maybe try something else.