Cheat mode
At the main menu, press Circle, Left, Right, Circle, Up, R2. You can now choose ''Cheat'' at the options screen where you can choose God mode, All weapons, Infinite ammunition, Infinite oxygen, No chestbursting, and Level selection.
Research mode
At the main menu, press Square, Up, Down, Circle, Left, R1. You can now choose ''Research mode'' at the options screen.