AS I have no idea what bits you are trying to revert, it is basically impossible to try and offer a meaningful comment.

Perhaps elucidate exactly what it is that irks you. Lots of it irk me, but I am making progress on some features like the menu location with the help of others.

OK, I was running LinuxMint. LinuxMint had some updates. One of those updates was Version 115.3.1 (64-bit). I clicked yes, to install the updates. When I started up Thunderbird, I found right away that I don't like this version. I went into Synaptic and uninstalled this new version, and reinstalled the previous version of Thunderbird. When I run it, it cannot use any of the mailboxes that I have, saying the files had been updated by a newer version of Thunderbird.

So, My question is, Can I get the files reverted back to work with the previous version of Thunderbird?

You can force the use of the profile with the command line switch discussed in the relevant support article. What that does in regards to backwards comparability of file formats is nothing, it just forces the use of the profile as it stands. There is no, nor any intention going forward to, support backwards compatibility.

https://support.mozilla.org/en-US/kb/dedicated-profile-thunderbird-installation

I've fixed it. I do a clonezilla image every 3 days. I restored back to my last image, which was yesterday. So, I only lost today's emails. Mostly spam anyway. Set synaptic to ignore future updates for Thunderbird. Thanks for the help.