How to permanently disable auto updates?

Hey again

I use Firefox Portable 55.0.2 on Windows 10.

I run a lot of windows of Firefox all day long on multiple computers, and going into settings and marking it to "Never check for updates (not recommended: security risk)" does the trick and my browsers remain on the version I need them to be.

But for some reason on a rare occasion a browser will update. I can't figure out why. Maybe if I click to turn it on and while it's turning on I click it again. I can't figure out why. And when that happens I have to delete the folder of that browser, put in a fresh one, login into accounts again, etc. Very annoying.

But it doesn't matter why it happens. What matters is that I would like my browsers to remain on the version I have them and never update. If the future of human life on earth depends on the browser to update, I want it to not update.

How can I "rip out" the updating capability of the Firefox portable browser (version 55.0.2) so that it never tries... or if it tries it fails to update?

Thank you