Press the following combinations of keys at the same time to
activate the corresponding cheat: 

All objects - Ctrl + Q + Left Click Mouse Button

Access all the screens/environments - Ctrl + M + Left Click Mouse Button

Get back to Elliot's room - Ctrl + O + Left Click Mouse Button

Increase ET's speed 3x - Ctrl + T + Left Click Mouse Button

Remove the objects from inventory - Ctrl + I + Left Click Mouse Button

Return to previous screen/room - Ctrl + B + Left Click Mouse Button

Stop all dialogue - Ctrl + W + Left Click Mouse Button


by unknown