Recently I updated my engine and now I realize that all libraries I used are not compatible with the last UE Engine. But the project has already been converted to the UE5.4.4 Is there any way to downgrate the progect back again, or it is not possible?
I remember I saw a notice that it will not be possible to downgrade it. Please confirm if it is true.
You cannot downgrade once a project has been upgraded, no. There’s a bunch of reasons for this, but they’re probably not worth going into here.
Generally, you want to keep backups—preferably through source control of some type—so that if something goes wrong you can just revert changes. This is especially true when doing something major like upgrading the engine version; even if you don’t have source control, it’s best to make a .zip backup or copy the project onto an external USB drive or something.
(I mean, it’s best compared to having no backup at all. Source control of some form would still be preferable.)