Villagers, Animals disappeared

I am using the snapshot and this version loaded automatically but didn't give the option to create a back up, all my villagers, domesticated mobs (including cats) and amethyst deposits have disappeared. I haven't checked stored items to see if amethyst shards etc are still there. Tried reloading the game but it didn't help.

**Update** Checked stored items, anything to do with snapshot has disappeared.

I have similar issues.  Was running 20w51a.  1.16.5-rc1 updated with no chance for backup.  It did say version was older but not sure how.  Lost all copper other items. 

That's what also disappeared in my world:

• frames 

• grass path blocks 

• boats

• cauldrons

All copper and amethyst were gone since 1.16.5 is not part of the 1.17 series, so you basically sort of downgraded. All path blocks are gone since they were changed to "dirt paths" in the snapshots and they had code changed. Cauldrons are the same with the new snow and lava ones. Boats and frames also had their code altered in some way.

Then an option to do a backup should have been presented.  I would suggest that is a bug.

See MC-211308.

There was no option to backup.  That is a bug. 

Yup, I created another bug report for that → MC-211381