Gary, if you are still following.
There is an excellent summary in the Wiki, see section 14.5 . If you do not breach any of these rules, your award wil lock in as a OWA.
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Here is an itinerary for 34,984 miles (Qantas figure may differ slightly):
Singapore-London-Brisbane-San Francisco- Brisbane (+ notional/equivalent miles back to Singapore).
You would need to make additional arrangements outside of the OWA itinerary to get to Singapore to start the OWA and to commute between Brisbane and Melbourne.