I like flying and I don't mind doing a multi-segment travels... I got invited to speak at the conference in Singapore, so I am looking which way to go. I've flown with BA before and BA direct is OK, but how about other options (sadly Y only):

1. Qatar: LHR-DOH-SIN-DOH-LHR
+ never flown before QR
+ DOH-SIN-DOH operated by A350

2. Finnair: LHR-HEL-HKG-SIN-HEL-LHR
+ never flown before with AY

3. Qantas: LHR-DXB-SIN-DXB-LHR
+ never flown before with QF's A380
+ never flown before with EK

Note: I am BA's Silver:
* would I have access to the lounge travelling on QF ticket operated by EK?
* I can select premium seats on A340 when booking with AY, would QR allow me to select seats at the upper deck in their mini cabin at the back of A380's?

Many thanks in advance for your help!