1)Qantas is subject to Australian regulation, other airlines may not have the same restrictions.
2)Qantas does fly to JNB and South America and hence need aircraft that can cover those requirements.
ETOPS is not local regulation. QF fly a mixed fleet and chhose aircraft according to route so that would not preclue B777 for some routes and B747 for others where ETOPS makes the route too long
Finnair have more Asian connection points than HKG.
They fly from BKK,SIN,NRT,KIX,ICN,PVG,PEK so lots of options.
Having recently used QF for a code share to connect to another OW airline in the far east I would not recommend using them for the sector from/to Aus. Really second class treatment.