Changing Clothes:
Finish
the game and rescue the other 2 players. A phrase that "You've got a
special key" will show up in the game's credits. Save your game and reload
with the game you just saved. Go to the room with the large mirror on the
second floor and unlock the door in the back. Go to the closet to find your
new outfit.
Get a Rocket
Launcher:
Finish
the game without using any saves