I have a economy cabin ticket BKK/NRT/SFO/LAS (all UA metal) with an SWU applied, and the last 2 segments have cleared. Still in Y for the BKK/NRT segment.

The saver F 1-way award BKK/NRT is only 20000 miles.

I was thinking of getting the 1-way saver F award on the flight for which I'm waitlisted, as a backup in case my upgrade doesn't clear.

If the upgrade cleared, I could cancel the award, but if it didn't, I'd want to use both of my tickets on the BKK/NRT segment.

I know people can purchase 2 tickets on the same flight, but do they need to be in the same cabin and next to each other?

Would I be able to scan both tickets as I boarded the plane, and then sit in the F seat? Would I still get the RDMs/EQMs for the paid Y ticket, and avoid my NRT/SFO/LAS segments from being cancelled?