Successfully complete the indicated task to unlock the corresponding character 
in Free mode:

Amy Rose            : Successfully complete all Soleana mystery missions with an "S" rank.
Blaze the Cat       : Successfully complete all Soleana mystery missions.
E-123 Omega         : Successfully complete all GUN Commander missions with an "S" rank.
Knuckles the Echidna: Successfully complete all Town Stage missions with an "S" rank.
Miles "Tails" Prower: Successfully complete all Town Stage missions.
Rouge the Bat       : Successfully complete all GUN Commander missions.