Finish the game and your partner level rises to 4 in arcade mode. Finish it 2 times and it rises to 8
In the beginning of the game press start, hold L1 R1 L2 R2 and press:
up, down, left, left, up, right, down, left, right, right, circle, square, x, x, up, down, triangle, left, down, up.
This will give you the ability to fly.
Finish Inferno mission 6 to get Chris with a Linear launcher and unlimited ammo
You have to finish the game using Roach mode.
You need to be in dungeon mode finish the 1st mission.
Get all messages in each level to unlock the secret report