If you are prompted to choose between "Local" and "Server" saves, always choose the one with the higher level or more recent date to avoid losing progress. Are you seeing this exact text in an error message, or are you trying to manually edit your game files?
If an event has ended, the associated items often remain in your inventory. These can usually be sold or removed. user blob farmville 2 upd
If you are playing on Android, you can locate and back up your file manually to prevent data loss before a major patch. If you are prompted to choose between "Local"