Flight Changi Airport departs from Singapore Changi Airport at 20:10 and arrives at Sydney Sydney Airport at 06:05.
The flighttime is about 7h 55m. The distance travelled ("as the bird flies"): 5577 Km. So the average speed is roughly 704 Km.
There is an 2 hour time difference between Singapore and Sydney
The best day to arrive at Singapore is Monday and it would be best to avoid Saturday, as prices are on average 137.06% higher than on Monday. (Average prices, based on 395985 datapoints.)
We have a lot more statistics for flights QF 84 and between Singapore and Sydney.