How to use the cheat to unlock all difficulties.

[Maximus 1482]

I got the cheat to work but dont know how to change the difficulty. i think im still on easy. what am i doing wrong.

[msc 10]

Start a new game and choose a difficulty.

Than go t de last chapter en choose the checkpoint 'Magruder's Mine' level part 2. You only have to play this checkpoint 4 times to unlock the achievements