Originally Posted by
Rosenstrauch
I mean, not really. The only time we know of that a character has 1. "Traveled to the past" and 2. "Rewritten history by doing so" was with G'raha. And he never even tried to go back, nor did he ever talk about the possibility of doing so.
For all we know taking the portal back could have worked like Trunks's time machine in DBZ. We could have knocked the past so far off course that our own future will never be possible from their perspective, and still arrived in our own future regardless.