9e7742db_ime_manipulation___Heroes_Wiki__Theory
[Citations] Since a traveler from the future cannot change the past in a way that would prevent him going to the past to change it, Hiro found it necessary to imbue one in the present with the knowledge that could change that. [Notes] + Hiro is at least somewhat free of normal space/time continuum rules. But not completely. By learning of the future and then going back to his original time, Hiro retained free will and can now actively work to change to future. + This helps with the "rift" problem that Hiro alluded to with Peter. By traveling to Peter and Hiro exclusively, beings who possessed his power and by extension his immunity to the "rules", he was able to change the future and quite possibly, eradicate his existence. Because the past Hiro knew of the future, the knowledge remained in place even without the Future Hiro having to necessarily exist. [Theory] 
Future Hiro could only change the timeline by warning his past self.
Theory:Space-time manipulation - Heroes Wiki
Theory