A lot to sift through here, however the process to exit HKIA after entering the departure area seems clear enough.
My biggest questions is, what's the risk of doing this? Almost every data point on this thread is a successful exit of the airport from the departure area after a lounge visit. Has anyone been told no? Or been refused entry back into the departures area?
I have a 14 hour layover coming up in a couple weeks that will start at 5:00 am (well before Disneyland opens for the kiddos).