Unlocking Oscar :
Finish the game getting a A rank in all levels.

Unlocking JJ Sawyer:
Finish the game getting a S rank in all levels.

Unlocking Naomi:
Finish the game getting a B rank in all levels.

Unlocking The Insider:
Finish the storage level getting a B rank.

Getting New Outfits:

New Kat Outfit - Finish score attack mode with high scores in all levels.

New Ethan outfit - Finish stunt attack mode.

Getting Stunt Attack Mode:
Finish Story mode.