To unlock all areas, you have to create a new profile named AccessAllAreas. Actually, there's an alternative way to make this cheat. Just edit the preferences.txt file by adding the following line:
UserProfile = AccessAllAreas
To unlock map editor and mod player, open your preferences filewhich is in the root folder of the game by placing the ModSystemEnabled = 1 parameter there. Then, start the game and press escape. After that you will find MODS option in the menu.