You commented about how going back in time and killing one’s grandfather would not uncreate the self, because once a person is created, they can interfere with the past and not undo their existence. Does this mean a person could go back in time and kill themselves at a younger age and not cease to exist?

This is quite true. It, in fact, would pose no problem for the person already in existence because the same reality holds true, that once created, the person is in existence and nothing else will matter except something impinging on them directly. In effect, they will have many prior selves going back through the reach of time into many previous incarnations that could be visited and explored and potentially modified for better or for worse. As you can imagine, this would be quite a complex undertaking with the intention to do an alteration of things affecting the person who is the time traveler involved, but it can be managed, and this is done by the aliens all the time and is quite routine.