I've uncovered clues about the two keys, three boulders, and three levers during the disc 1 dream sequence. Yet, even on disc 3, a perplexing red door remains locked.
Venturing through elevator 1 and veering right before encountering Mobile Type 8 leads to a door seemingly connecting to elevator 3. My theory is that accessing the other side of this door from elevator 3, then proceeding right, may reveal further revelations.
