After unlocking the seventh night, you can change the AI of any animatronics (excluding Freddy Kim) from 0 to 20.

Defeating 20/20/20/20 unlocks the third star. In order to beat 20/20/20/20/20/20, you need to be very fast and efficient. Perform and repeat the process: go to the corner of the East hall. Pull the camera down. Look at the door light on the right (if it needs to be closed). Look back at the camera. Pull the camera down. Look at the hall lights on the left (if need be turned off). At the end of 20/20/20/20, you will be fired and awarded a third star.

Fox and Freddy won't kill you unless you stop staring into the corner of the East Hall, because Freddy will sneak into the room. Foxy won't kill you because there are cameras, it won't kill you, and if you move fast enough, it won't have a chance to move. You shouldn't use up all of the above strategies, and if you do, you won't die because it's almost 6 a.m.