Board Thread:Questions and Answers/@comment-30300307-20170426071235/@comment-477304-20170427014616

The only alternate timelines that have been shown in the Sonic series are in Sonic CD with the bad future and Sonic '06. You can argue that the entire game is set in an alternate timeline as as the course of history was changed when Elise blew out Solaris. Silver might exist in an alternate future as well as changes made in the past didn't seem to save his era from Iblis. As Silver was partly inspired by Future Trunks from DBZ, it may be that time travel works similarly in Sonic '06 as it does DBZ, but that is speculation.