For infinite health, die at the same time you kill a Boss. This is best done when fighting Revenent Prime. Get him down to very low health and wait until he starts to destroy the building you are standing on, then let him have it. As you fall to your death the game will continue to show a short cinematic sequence, and you will start the next level with 0 health. Enemies cannot kill you, but you can still die if you fall off the level. Note: The health warning will constantly sound.
Note: This procedure requires editing a game file; creating a backup copy of the file before proceeding is recommended. With a text editor, edit the "szOptions.ini" file in the game directory. Examine the entries under the "[Settings]" heading and change:
Game Mode=1 Gallery Mode=0
Game Mode=0 Gallery Mode=1
Begin game play to have unlimited ammunition. Additionally, press R to fly.
Press T during game play, then type /debug on. Then, press CTRL + ALT + 7. The message "Game mode off" will appear to confirm correct code entry. Then, enter one of the following codes to activate the corresponding debug function.
CHEAT FUNCTION - CHEAT CODE Extra ammunition - CTRL + ALT + 5 All weapons - CTRL + ALT + 6 Ignored by enemies - CTRL + ALT + 3