If you hover over the project name in the upper right you’ll see the ChangeList number.
For UEFN (24.40) I’m currently seeing 25420516
And for 5.2.0 I’m seeing: 25360045
Work is done in ‘Branches’ - For example 5.2 branched off of the Main branch a while ago and was tested/stabilized. Then the fixes would be merged back into Main (or fixed in both branches simultaneously?) .
There are going to be a lot of other considerations for moving UEFN assets to 5.2, but like you said - It’s not possible to open ‘newer’ assets in an older engine version. (And this is based on ChangeList number)