Do all A330MRTTs have a main deck cargo door?
Those for the nation that asked for the main deck cargo door have. The USAF's would have too.
Do they have a main deck floor designed, stressed, and equipped to handle freight
Not required - can carry 45 tonnes of freight in the underfloor cargo area. This is something the KC-46A can't do this as much of the underfloor space is taken up with auxiliary fuel tanks, which would be why most of the cargo needs to be carried in the main cabin - a case of the aircraft's capabilities dictating the requirements, rather than the other way around.
Do the UK's Voyagers?
No, see above.
Can the A330MRTT 3D camera vision system enable the boom operator to pass gas to receiver equipped stealth aircraft under all lighting conditions?
Australia is the only current 'boom-MRTT / F-35' operator, and I have heard no reports from the RAAF that it can't.
Can the A330MRTT act as an airborne data relay station for stealth aircraft equipped with directional datalink systems?
See above.
I could go on, but I think the point has been made.
I'm not sure
what point has been made. None of these things - the reinforced floor, the ability to fuel stealth aircraft under all lighting conditions or the ability to act as an airborne data relay station - are the reason why the KC-46A is so massively delayed and over budget. It is telling that nowhere did you ask if the MRTT has had a fully functioning fly-by-wire boom for the last 11 years.
They could not match Boeing's low-ball bid. Just as Lockheed and several others could not meet Boeing's low ball bid for the T-X trainer (with a EUROPEAN partner), nor Boeing's low-ball bid for USAF's UH-1N replacement (the only bid based on a EUROPEAN helicopter), nor Boeing's low-ball bid for the MQ-25.
I do agree with you on this, but it's a slight divergence from the operational requirements/ merits of the MRTT vs the KC-46A in relation to the KC-X contract award and re-award.