The earliest version you can move back to without seeing the error is 3.03 (as shown in this table).
Reverting can be done but it involves deleting all your local Joplin data and downloading all your notes again from your WebDAV sync target. The downsides of this are that if you have lots of notes it will take time. Additionally you will also have to setup your plug-ins and customisations all over again.
If the issue for which you are wanting a fix is present in both the current version (2.14.22) and the latest pre-release version (3.0.8) it's probably worth just sticking with the pre-releases until v3.x is declared stable. Speaking of which, v3.x development is due to go into "freeze" soon with a planned publishing date in the first week of July.
Is the fix you are looking for related to a known issue? If not it may be worth explaining what you have found in an issue on GitHub (or a new support post here). Then the devs are hopefully aware of it during the "freeze" as that is where adding new features is halted and they concentrate on performance and any remaining bug fixes.