A1. There is a "sterile" requirement between inbound and outbound passengers - same applies to all flight crew. "Never the twain shall meet" or at least on the tarmac, aircraft, or not having first cleared CIQ.
A2. Crew lanes are a privilege, at least in Australia, so if you have a crew lane, and it is "manned" (sorry, tried for a non-gender specific term) this is your lucky day. Sometimes, if there is not a crew lane, then you can be acknowledged and moved to the front of the queue; again this is your lucky day.
A3. The program is the TRS - TOURIST Refund Scheme. Simplistically, if you are a tourist (or crew member) travelling with a valid ticket and boarding pass for a seat, AND you are not on the GENDEC, then generally, you are entitled to the same GST refund as a normal passenger (tourist). See this URL:
Advice for travellers
Somewhere in the fog of my memory, it was decided that for flight crew to be restricted to only 2 bottles or the usual passenger allowance, each ten days was discriminatory, and was scrapped. Hence, we now have the same DF allowances as a passenger. Ten flights a month - no restrictions, at least on the DF side. As for Crew Articles in Possession and allowances for goods, that is something else.