To unlock a harder difficulty complete the game with all 'A' ranks and all 141 emblems.
2 Player Team Battle Mode:
Get 20 emblems in the 'Single' player story or 'Challenge' mode to unlock.

Unlock Two Player Special Stage Mode:
Get 40 emblems in the 'Single' player 'Story' or 'Challenge' mode.

Unlock Two Player Ring Race Mode:
Get 60 emblems in 'Single' player 'Story' or 'Challenge' mode.

Unlock Two Player Bobsled Race mode:
Collect 80 emblems in 'Single' player 'Story' or 'Challenge' mode.

Unlock Two Player Quick Race mode:
Get 100 emblems in 'Single' player 'Story' or 'Challenge' mode.

Unlock Two player Expert Race mode.
Collect 120 emblems in 'Single' player 'Story' or 'Challenge' mode.

Unlock Metallic Characters in Single Player mode:
Collect 141 emblems in 'Single' player 'Story' or 'Challenge' mode.
Unlock Follow Me Song:
Complete 'Story' mode as Team Rose.

Unlock Team Chaotix Song:
Complete 'Story' mode as Team Chaotix.

Unlock This Machine Song:
Complete 'Story' mode as Team Dark.

Unlock We Can Song:
Complete 'Story' mode as Team Sonic.

Unlock the Team Chaotix FMV:
Complete 'Story' mode as Team Chaotix.

Unlock the Team Dark FMV:
Complete 'Story' mode as Team Dark.

Unlock Team Rose FMV:
Complete 'Story' mode as Team Rose.

unlock the Team Sonic FMV sequence
Complete 'Story' mode as Team Sonic.