re: Qantas "oneworld" award (140K/280K/420K) Discussion
Certainly, you could not return to SIN except at the end of the routing.
Also there are the transfer/stopover constraints so you cannot transit any port more than twice nor stopover more than once, nor have more than five stopovers.
I believe this would be a valid ex SIN route:
SIN-xHKG-MEL-xHKG-NRT-SYD-HKG-BNE-xMEL-SIN
