OOL to CNS direct, while you can book the award at the QF website, it will be on JQ plane.
18,000 points, yes, that would be right, OOL to SYD is 8,000, and SYD to CNS (both on QF), would be about 10,000.
There is no such thing, as if you fly from OOL to SYD to CNS, its going to less than 18,000. I thought it was 24,000 + $$ when I did the look at it, OOL to SYD to CNS.
Just too complicated to play around like the way you are thinking, just "bite the bullet" and fly from OOL to CNS direct, for 9,400 + $41.
Thats what I would do, and not fluff around going backtracking to SYD, and "hoping to use only 12,000/18,000".
If you really want to fluff back to SYD, to get the 767 from SYD to CNS, which i might do, if I was going P+P, then I would "probably" backtrack to SYD.
Off topic: I love wide bodied planes. Pity to see the day when all the 767s are gone, and the 787s all going to JQi. From what I look, the 330 are also not that many in number.
PS, and yes, I talk too much bull.
Do what you want anyway, and best of luck using the 12,000, (or less!).
I am not that well taught with MASA, JASA, XASA... and all that.
Airport codes I get, MASA, JASA, XASA, I don't.