Not to my knowledge. If, however, QF are actively trying to move people onto earlier flights due to, for example (1) approaching bad weather, or (2) cancelation of the late / last flight, then you might have a chance of such a move forward. If you have high status, you might get more of an audience (in the Qantas Club lounge) if you make the request - otherwise I wouldn't expect anything.
Agree in general, but on high frequency routes like SYD-MEL, I have several times (on reward tickets) been but on an earlier flight when checking in. I suspect the rationale - what if later in the day there are issues (weather, mechanical, others with misconnections, etc) then it is better to fill up the earlier aircraft. These routes have 767s and A300s.