SQ and CX into UAE
As far as SQ flights into DXB and AUH, they do a lot of freighters but have also over the years operated passenger SIN - DXB - CAI and SIN - AUH - JED returns on B777 and A330. Don't know if that is still happening. CX used to operate a HKG - BOM - DXB return on the B777 a few years ago as well.
With the UAE open sky policy it seems that any airline can operate through DXB/AUH to wherever they want, am not sure of fifth freedom rights though.