As above in Australia
- international arrivals
- international departures
- domestic departures-arrivals
are physically separate. Are 3 distinct areas.
You can only access the MEL T2 international departures Qantas First lounge if you have a boarding pass/security/immigration check for a flight from T2 international. Are a very few limited AU domestic flights from the international departure terminal.
As above, T2 to T1 QF domestic is a 3 minute walk and up 1 level.