complete The game with all characters.
To get dark sonic you must beat the game with every character in the game S.F.G.X.That unlocks mission mode. Beat mission mode and dark sonic is yours if you have trouble go to the youtube user marjosonic and start at video 9 or 8 [I forgot]
Dark Spine Sonic is not a playable character although you can play as him only as a custom character using gamemaker 8. More information~ Darkspine Sonic isn't a playable character. But you can get the Custom character of him by joining the FGX Insider(SFGX's Forum) and posting 150 times.
you just type :sonic fgx download:
sonic 5
hkskjt5 sonic fgx 2 games is all rig
RFRHYGNH
a+b
NO
Collect all chaos emeralds.
Play as sonic shaow and knuckles
media fire.com
you cant do that