Can't find level I worked in UE5.1 on UE5.0.

[Cytokinetik]

Also try this script if you need to downgrade a project, if it is your only copy.

How to fix : uasset has newer custom version of FortniteMain?

I found this blog post which includes an engine version downgrade script. I discovered that it actually works most of the time, even with blueprints. Most of the assets will become visible within previous engine versions. It is then required to right-click or bulk select the assets right-click, and resave; with blueprints one can do the same, or open the blueprints and recompile/save. Tested with several engine versions. Just change a variable or two within the python downgrade script, as noted…