Originally Posted by Mwenenzi

Same or separate tickets/PNR? Done the T1 T3 shuffle before?
If 1 PNR all the risk is with QF. If QF12 is late they may put you on a non direct flight BNE MEL (if such a flight exists).
06:35 to 08:25 = 1:50 hr to transfer will be tight.
Look at this thread --> Does Qantas offer goodwill flight change if I miss the flight? Was OK, with time to spare.

QF are having some reliability issues with long haul flights and not enough wide body aircraft in service. If an aircraft goes tech can take days to catch up.

https://www.flightaware.com/live/flight/QFA12
https://www.sydney-airport.net/syd-arrivals-terminal-1
FT-->Airport info SYDNEY (SYD) - amenities, transfers, transport