I tried preview datapack on my world, but when I tried to disable it and return to previous game version without this datapack. The world opened, but every block in it has been regenerated. All my builds were destroyed. Entities - mobs and items - stay on their positions. If I want to play my world still, I need to play with datapack, because I havent any backup before switching to datapack. I have only backup after switching, but its still good. Thanks you