I am travelling from SYD to SIN on QF ticket and metal, then switching to EK ticket and metal for an onward flight.

I am travelling from SYD to SIN on QF ticket and metal, then switching to EK ticket and metal for an onward flight. In light of the Qantas/Emirates alliance, will I be able to check my bags all the way through to my final destination despite travelling on separate bookings/tickets or will I need to clear immigration, customs etc. then check-in again at Changi? Thanks!

Seperate booking=having to recheck in and clear customs/immigration at changi

I flew with separate booking numerous of times, as least half a dozen. As long as you with same alliance, say OW and you spend less then (I think) 20 hr in transit it is no problem whatsoever.

You better clear CIQ and collect your bags to recheck.

Yes. Can confirm it's the case, QF will check through the bags from SYD onto your final destination, provided the other itinerary is all EK (or OW). You will still need to pass by the airside transfer desk at SIN to have EK enter the baggage ID into their manifest.

If it is QF ticket on EK metal then I fully agree with you - this is what happens to me anyway. However OW (AY in particular) incredibly reluctant to check through with EK (they not member of OW, damn Qantas to make this stupid agreement!) and for sure will not do it with "pure" EK ticket and metal. Qantas may be different though with their live to EK. To OP - if they say that it is impossible, do not give up, demand supervisor and be persistent. JQ (QF ticket) reject check my baggage through to AY in BKK saying that BKK disallow overnight baggage staying. I came to other counter and guess what? They did it. Same happens with AY - when they reject check it through to Oz because EK connection (QF ticket though) and said that it is “absolutely impossible” and “system will not allow it”. Then I demanded supervisor and asked her to try instead of feeding me with stories. As result they did it. Never give up, but do not be rude. Good Luck.

Does't have to be a QF ticket. It's irrelevant. It can be on a VX stock, as long as the operating carrier is EK, QF have agreements in place to support interlining with EK.

Perhaps in this regards QF differs from OW. I would guess so anyway.