Any project files saved with 8.1 will be incompatible with the older version. You will need to restore a copy of the older 8.0x file from TimeMachine(or other backup) and reapply any changes made.
Any project files saved with 8.1 will be incompatible with the older version. You will need to restore a copy of the older 8.0x file from TimeMachine(or other backup) and reapply any changes made.