Loading 20w51a world in 1.16.5-rc1 issues

• no "create snapshot & load" option any more, only "load"
• all villagers despawned
• all passive mobs (sheep, pigs, striders etc) disappeared / not spawning
• all copper items in inventories & placed in the world disappeared
• dripstone, spyglass, amethyst, tinted glass, candles (in inventory as well as placed in the world ) disappeared, including naturally generated features like amethyst geodes (see attachments - before & after the update)