The butterfly effects would add up and and any zygote formed would not be the hitler-as-we-know anymore, since it would be a different combination of sperm and eggs.
Who needs guns when you got a time machine? Don’t like your highschool bully, just bump into their parents back in time. Or you know, “bump” ( ͡° ͜ʖ ͡°) into their parents.
Many worlds theory gives us an alternative - in one world I left my phone in 1929 and that shaped that world tremendously.
But that didn’t happen in my world and it can’t, because my world is the world where no one left their phone in 1929.
Yes. There are many paths forward from any moment in time but only one path backwards. That means that to get to where you are right now whatever happened in the past has already happened and can’t be changed.