There is nothing behind you(from picture prospective) on the fourth wall.
The door is metal like stage 1 but there is a handle and it is a classic orb shape, a rusty brown color and is also made of metal. (unless otherwise stated, pretty much all doors will be made of unbreakable metal).....I cant convey texture very well with MS Paint, but the celing is made of a very dark form of the wall "marble". It is not a container.
Walking to the door and "wiggling" the handle, you feel the doorknob jiggle and feel a springs resistance and a little give, indicating that the door is likely unlocked.
You find that you cannot tear your outfit to obtain such a thread. [Worry not:if your worried about loosing the coin in the slot you will be able to reach into the slot with your finger and slide the coin back out, Im not a total bastard]
You examine the gear train/track and find that there is no way for you to tamper(as in fiddle with) the gearbox or the track it runs.
There is motion and noise coming from Stage 1, looking down the hatch you see the spikes have completely closed and sealed the room.