Using cheats or hacks to unlock game content can be against the terms of service of the game. Developers usually discourage such practices as they can ruin the gaming experience for others and potentially create security risks.
However, players commonly use community-made to bypass the progression requirement: hitman absolution all missions unlock link
If you don't want to replace your save file, you can use a "Trainer" or software like to enable cheats such as Infinite Instinct Invisibility (Ghost Mode) Using cheats or hacks to unlock game content