The Grandfather Paradox. Classic time travel problem. If I had a time machine, I would get a year’s worth of lotto numbers.
If you don’t want to exist, just think, most likely there’s a parallel universe where you don’t exist.
And watching the universe being created would be cool, but the laws of physics didn’t quite ‘condense’ yet so your body might not even be able to exist. You would have to find a way to pop into ‘brain space’ where you could view everything, assuming your body (or anything for that matter) could exist there. Brain space is the space between 2 universes, theoretically membranes collide there and create a new big bang which leads to an isolated universe. If you wanted to transfer between universes, you would need to focus A LOT of energy in a VERY tiny spot in space to open up some kind of (possibly unstable) portal. All theoretical of course.
You know, black holes freeze time. So if you want to travel to the future, you can get really close to one (but outside the event horizon) and your time will be slower than that of the rest of the universe. So you just wait for however much time to pass in the rest of the universe and leave the vicinity of the black hole. Poof time travel.