Airline: Qantas
Alliance: OneWorld
When: winter and summer! Get in some late snowboarding at Whistler, or be in 'paradise on earth' (Vancouver in summer - note: I used to live there and summers are epic).
SYD: Direct to Vancouver
MEL: One stop in Sydney
Steps: Go to the flightscout links to see available dates. Select which you like, and click through to the skyscanner results. Often varies a few dollars (eg the ones I've described are slightly higher on the cached prices on flightscout, but cheaper when you click through).
Sydney flights: https://flightscout.co/au/cheap-flights/sydney-australia-to-…
Melbourne flights: https://flightscout.co/au/cheap-flights/melbourne-australia-…
Can always go through Thailand and seek asylum