Bumping this thread again as I have a very similar situation and had a few q's for the experts (I seldom fly EK, so not sure how this should work and what I should expect/not expect)

The basics: Have a multi-leg trip upcoming all booked and ticketed in F using JAL miles (JFK>DXB>SEZ>DXB>ATH>EWR, with stops in DXB, SEZ, and ATH. A few weeks ago I got a downgrade email on the DXB>ATH leg (equip change from 3 cabin to 2 cabin 777). I have spoken to both EK and JAL and because there is currently not F upgrade space on the earlier flight from DXB>ATH (which actually would be preferable timing, as we arrive early on a redeye from SEZ), they cannot change our flights. They also noted that they could easily change it if space opens up between now and the flight. Nothing abnormal there, have EF alerts set, 4 F seats are still avail on the earlier flight to ATH.

My two main questions:

1) If upgrade space does NOT open up, but F remains with open seats, can anyone on the ground make a day-of change to the 3-class/earlier flight, given we were involuntarily downgraded? Is there some sort of process for getting on a standby list once we are on the ground?

2) If the answer to question 1 is "no, they can't make such a day-of change given it was a partner award" (which is the vibe I am getting), can we still access the First Class lounge in DXB for our almost 11 hr layover? Would be kind of a bummer if that answer is also "no", given we were initially ticketed in F and were vaguely looking fwd to a nice layover in the First class lounge in DXB.

Understood that some of these requests may be at the discretion of the DXB ground team, but was hoping someone with a similar experience might have some real-world insight and advice on how to handle, if we can't make the change ahead of checking in.