Not without starting over or probably loosing something. Your profile is now a Version 115 one. You can force Thunderbird on an older version to use your new profile using command line switches when invoking Thunderbird, but any data that was converted in the update will be lost, not downgraded.

I suggest working to fix whatever you see as broken in the new version. I was trying to answer your other questions but this popped up first. Perhaps slow down a little because going back is not simple or convenient as you think.

OWL add-on is not working with 115.3.2 Any one have a solution?