Did you perhaps write in those Spine version numbers manually?
I deleted Spine folder before reinstalling, but the versions menu showed same contents.
Was this folder the Spine installation folder, or the user home folder?
User home folder:
Windows: %UserProfile%\Spine
Mac: <user home folder>/Library/Application Support/Spine
Linux: <user home folder>/.spine
You could try renaming the "updates" folder and then start Spine. It will look for the latest version of Spine then. If you need a previous version, you can then enter it in manually.
Spine actually never sorted the versions, so I've created an issue for it here
Sort version numbers under Spine Settings · #492 · EsotericSoftware/spine-editor