Press T to enter talk mode during game play.
Once there just type any of the following:
ammo = Gives full ammo
god = Gives god mode
guns = Gives all guns
Access All Chapters
To open all chapters of the game, run REGEDIT and find the key: [HKEYLOCALMACHINESOFTWAREMonolith ProductionsContract Jack1.0]
Change the value of "EndGame" to 1. Note: Always make a backup before editing the registry.