The first is the 'zinger' question. If I knew, do you think I would say ? :mrgreen: . Seriously, almost impossible to know. People around here have their 'favourite' airlines and, importantly, routes that they like to redeem on, but the availability of Award seats is not necessarily fixed; an airline might quietly withdraw reward seats if their regular ("revenue") bookings are heavy for that flight.
if you earn Qantas points, then that gets you access to all OneWorld Airlines' Award seats and also Emirates ; you book them through the Qantas site. I've never tried myself but you should be able to go via HKG on Cathay or a combination of QF, CX, AY and BA. Frankly its been years since I redeemed on Qantas so I'm a bit out of touch.
People also use the BA FF program/web site and/or the JAL FF program/website to search for Award seat availability across OneWorld, as the QF one isn't very good at it. Again, you'll have to take time and absorb all this through the threads here. Also have a look at the AFF 'Knowledge Centre'. Again, don't use it myself but you pay a bit and get a distillation of knowledge on certain subjects.
With Virgin, you get access to them and partners of which
Etihad is notable in getting to Europe.
Have a look at threads involving Expert Flyer. I don't use it myself but its a (paid) tool that reveals exactly what seats in what classes are available on almost all flights.
Lastly., on this aspect, have a look at the American Airlines and even Alaskan Airlines FF programs. They allow you to 'buy miles' and a number of times a year they have bonus offers. EG Buy 70,000 miles and American might give you 35,000 bonus miles. The cost on AAdvantage is often about US2.2cents/mile. Then you book through the AA web site for AAward seats. They also have
Etihad as a partner and going First on the A380 out of Sydney to DXB and onto LHR has been popular here. When the US$ and A$ were close, it was an absolute STEAL. Now with the A$ devaluation and AA about to jack up the number of miles required, its marginal. But if you have access to US$ its very much worth a look; wait for the bonus offers; go through the AA threads.
Alaskan isn't part of an alliance, so have many 'partners' so you can go a long way redeeming their miles for flights through them. Again, they have bonus offers and again, there are threads about AS here.
To know the cash cost of an award seat, you need to make a dummy booking, but I'm not sure if you lack the required points it will allow you to proceed. I had a quick look next April and could only find seats on Emirates via the Qantas site. Cost for J was $620 one way, one person in addition to the points. A pure Cathay flight via HKG in November was only $128 in cash extra (this surprised me). Qantas to LHR then BA to FRA in November add $744 one way to the points cost.