I had a world in 1.14, and I loaded it in 1.16 to use the /locatebiome command. I was far from my home, and I loaded it back in 1.14 to see all of my creations were gone, my 16 weeks of work all gone. I tried to make a backup before, but it crashed my game, so the backups never completed. I'm on java edition, please tell me if there's anything I can do.
No, there is no way for you to get your world back entirely the way it was without a manual backup, as Minecraft worlds don’t automatically back themselves up. The reason for your world’s corruption is because after loading a world of a newer version in a world of an older version, the game can’t properly load in the new game assets, as JSON elements don’t exist for the new items and the system can’t handle the new enchantments, as it isn’t set up to handle the new NBT tags properly. In conclusion, if you want to avoid this issue, simply don’t open later worlds in an older client.
Well in order to restore a world you have to have a backup. That is why it makes a backup of the world every time you open it in a different version.
Double check and make sure you actually dont have a backup. If you dont have a backup, I'm almost certain you'll have to start anew.
You should be able to find your backups folder in your minecraft game file, but I'm not at a PC right now so I can't check.
Hope this helps.