Why would I have to do that to achieve immortality? Undoing the chain of causality is not necessary. Anyway, here goes. According to a fringe theory based on the amplituhedron, space and time may not be fundamental, but emergent. If they are emergent properties, then with an understanding of what lies beneath, then perhaps within a particular system, such as a universe, maybe we can one day manipulate the causality chain and operate from a more fundamental position. It would be like if you had a sheet of paper and had flat landers living on it, and they wondered about the impossibility of finding their way out from the inside of a circle. From their perspective, they can't ever do it. But you, being a 3 dimensional being could imagine picking them up into the third dimension and setting them down outside the circle.
Space, time and causality chains may be the same to us here. Isn't that the nature of science fiction and fantasy? In just a short time, much of what was unthinkable becomes ordinary fact. Its happened countless times with paradigm shifts, scientific progress and general technological development. I see no reason to think or accept that the limitations of today will be the limitations of tomorrow, or a million years from now.