You have to make sure to turn off auto-update
before quitting for the first time. If you quit and restart Fx102, it will instantly update to Fx115. Even once auto-update is turned off, it will still prompt to update every day or so, and a single misclick applies the update with no confirmation. Very hard to stop Firefox from updating these days.
(Two things that will soon make this less arduous: one, we’re working on
embedding the devtools so that you won’t need a specific Firefox version in order to inspect/debug; and two, we’ll have Zotero running on Fx115 soon.)