Finish hard mode in infinity mission.
Acquire Naked Snake:
Finish easy mode in infinity mission.
Acquire Roy Cambell:
Finish extreme in infinity mission.
Acquire Old Snake:
Finish Medium mode in infinity mission.
Acquire Boss Rush Mode:
Save the game on your PSP memory stick for the original Metal Gear Solid: Portable Ops. Begin a fresh game on Portable Ops Plus with the original save data to acquire this special mode.
