I did exactly this. Too many defects with the FS 2024 SR22T, so I disabled it. I own Premium Deluxe FS2020, so it automatically subbed in the FS2020 version of the aircraft - even warned me about it.
Note you have to explicitly disable the newer version in order for that to happen.
And how would I know there’s even a conflict in the first place?
When I rebooted after enabling aircraft from the first version, there was no indication that I was trying to install (or enable) two different copies of the same aircraft or scenery object.
I recognized that the Cirrus (Y-tail) jet already exists in 2024 so I didn’t enable it, but I make no bets for any other aircraft, (except for the Rutan Long EZ which I know 2024 doesn’t have.)
I did this as well, for the 2020 Premium Deluxe 787-10 in lieu of the 2024 version. I did so because the 2020 version has Simbrief integration, while the 2024 version doesn’t (apparently Asobo wants you to use their integrated flight planning tool which I find to be unsatisfactory).
There wouldn’t be. The sim by default will do two things:
If there is a 2024 version of 2020 content, it will default to the newer version being Enabled and Disable the older one.
If the vendor tells MS my 2020 product is not 24 ready or MS hasn’t received explicit approval from them - it will say Disabled, not Vendor Approved. You will need to enable it.
So there’s no danger of two exact versions of the same SimObject being in play at the same time.
Pre SU1 I found it didn’t work. You needed to explicitly disable the newer version. Since I joined the Beta, I have made no such changes so I can’t say it’s the same behaviour now.
AFAIK, an Xbox account can only run one version of the game at a time. For MSFS 2024, this means (at the moment) one can choose to use either v1.2.11.0 (RTM + Latest Hotfix) or v1.3.7.0 (SU1 Beta).