Undo saved changes made in .aup or .aup3 file

I am using Windows 10 and Audacity 3.2.1
When I first started using Audacity I saved all my vinyl recordings in the .aup or later in the .aup3 format. I then made changes to the recording, (click removal, noise reduction, etc.) and saved the work to the .aup or .aup3 format. Now after using Audacity and learning more about it I want to go back to these recordings and redo these vinyl recording. But it appears once you save the .aup or .aup3 all changes are permanent.

It would be a major undertaking to re-record the hundreds of records I have already completed. Is there a way to delete the changes in the .aup and .aup3 files, returning them to the original unaltered version.

Indeed that is the case

Sorry, but no - Audacity does not store the undo information with the saved project so you cannot revert.

When I converted my LPs and singles I always as a first thing I did after recording a side of an LP was to export a WAV file of the recording so I could always go back to importing the WAV if I got dissatisfied with my editing.

Peter.

Thank you. I was afraid of that. Oh well live and learn.