Has anyone successfully opened a QuickBooks file or backup in a prior year version?

Long story short, my client has QB 2020 and I used QB 2021. Now we cannot get the file or backup to open in 2020, since I did all the changes in the 2021 version.

Yes, I can re-do all the changes in QB 2020, but that is going to be very time consuming. 

QuickBooks - Please make it possible to tell which version a QuickBooks file is, or make it possible to open a backup file in a prior year version.

Not having one or both of these capabilities is just bad business practice when your only solution is to upgrade to the newer version. You can open backup files in newer version, you should at least be able to go back to a version previously used.