UE4 is notoriously bad for reversals. When you update the project, the old project is destroyed and replaced by the new one. So even if you downgrade the engine back to 0.19, the project's metadata is 0.22 and incompatible. So, you'd lose the entire project if you tried.
In fact it is so bad at reversals, with it's metadata, that even deleting an object from the game files can sometimes corrupt the project file. Happened to me... lost 7 months of work in an instant... that is when I gave up on UE4. It's metadata system is super finicky... much worse than Unity.
However, UE4 is free and has powerful graphics engine and well optimized to work on modern systems... whereas Unity isn't powerful and not well optimized. Not sure on Cry Engine though, but that requires a paid monthly subscription to even download, much less use.
So I can understand Wildlife's pain at the moment. They are quite literally stuck, and until they unstuck themselves, they are boned. That is why if I ever use UE4 in the future, I'll keep backups of the project file for each build, and have a backup of it in case I would decide to update the engine. Live and learn...