What a lot of questions. The Satellite 2 Domestic lounge has always only ever gone as far as it is on the middle level and the space directly above it has been unused since the building was built. A bit of a waste really, but they are looking at developing it for International use maybe next year. In the domestic lounge you can see the boarded off areas where the escalators were originally built to go up to the top level and down to the TTS station.
And the APV tunnel into the terminal links to some steps that come down from the Departure Lounge. That's so it can be used to get passengers to coaches if the TTS Train is not available.