The current version on offer should be 3.4 (although the release will be staggered as usual) … Feedback for v3.4 … /e/OS official FP4 download … perhaps 3.4 would behave better?
Backup everything important to you from the phone to a safe place and install the older version from scratch, wiping your data. Then set everything up again using your backup.
Android forbids simple downgrades for security reasons.