God mode:

Start the game and start playing any level
then type "iwillbetheone" and you will 
Become God.


All levels:

From the Main Menu screen, hold LEFT-SHIFT
and press the - key on the number pad. Let
go of both and then type the word campaign
to get all levels.


Finish Mission:
During play hold the [left shift] and 
[keypad minus] then let go, type "endmission"
to finish mission.