Enter all of these codes at the Password screen.

Play as Prey-t x t x o x s t t s o x
Play as the hunter-s x o t x o s t s x o x.
[Note after entering this code the sound will be turned off,so exit the game enter the options and turn on the sound now re-enter this code to play the hunter.
Play as the Raptor-s x o t x o s t x s o x
Play as the T-rex-t s o s x t t o s t t x.
After entering this code the sound will be turned off , so exit the gaame go to options and turn on the sound.
Now re-enter the code to play the T-rex.59 Lives-t x s t o x s o s t x o