Cheat menu:
At the main menu, highlight Undercover mode and press Up, Up, Down, Down, Up, Down, Up, Down, Up, Up, Down, Down. Now press Right or Left to activate the cheats.

Level Codes:

Level  Password
  1    faceX4
  2    tire mark, badge, cone, red siren
  3    stop light, keyX2, blue siren
  4    coneX3, bagde
  5    key, red sirenX2, stoplight
  6    key, badge, tire mark, blue siren
  7    badge, cone, badge, red siren 
  8    Red Siren, Badge, Key, Tire Tread  
  9    Cone, Blue Siren, Red Siren, Red Siren  
  10   Badge, Badge, Stoplight, Cone  
  11   Blue Siren, Key, Key, Key  
  12   Stoplight, Tire Tread, Red Siren, Badge  
  13   Key, Badge, Badge, Cone  
  14   Red Siren, Blue Siren, Red Siren, Blue Siren  
  15   Tire Tread, Key, Cone, Stoplight  
    

Thanks to Revolution readers jim, Justin Ingram, Budgie and leo Mellizo!