Beat any of the Story modes with 100% completion to unlock the 'extras' option at the main menu, which contains cutscenes and music from the game. Getting 100% on different episodes opens up new songs in the audio menu.
Play as Shadow The Hedgehog:
Beat the Crisis City level as Sonic.
Play as Silver The Hedgehog:
Beat Silver as a boss using Sonic.
Beat Sonic, Shadow, and Silver's Story modes to unlock a fourth Episode.
Get an 'S' rank on everyone's levels, bosses, and town missions to open up Free mode.
Extra Free Mode characters:
| Miles "Tails" Prower
||Beat all Town Stage missions
| Rouge the Bat
||Beat all GUN Commander missions
| Blaze the Cat
||Beat all Soleana mystery missions
| Knuckles the Echidna
||Beat all Town Stage missions with an 'S' rank
| E-123 Omega
||Beat all GUN Commander missions with an "S" rank
| Amy Rose
||Beat all Soleana mystery missions with an "S" rank
Thanks to Revolution Readers PhantasyFil, Kloud_99, and Doooog!