The minimum iOS version required early on was iOS 8.2

ex: https://www.mozilla.org/firefox/ios/1.1/system-requirements/ https://www.mozilla.org/firefox/ios/2.0/system-requirements/ https://www.mozilla.org/firefox/ios/9.0/system-requirements/

Then for Firefox 10.0 and later for iOS the minimum as been iOS 10.3 though best to have iOS 12+ to fully support features. The current Firefox version for iOS devices is 14.0 https://www.mozilla.org/firefox/ios/10.0/system-requirements/ https://www.mozilla.org/firefox/ios/12.0/system-requirements/ https://www.mozilla.org/firefox/ios/14.0/system-requirements/

There are no links for possible downloads in any of the target pages.

The downloads are not from Mozilla but from Apple App store.

The links I posted were to show the iOS requirements.

Apple only provides links to download the latest version.

Yes, unfortunately Apple controls all its apps like that.

Since we make our browser open-source regardless we post the source here: https://github.com/mozilla-mobile/firefox-ios/releases

Although I don't see a installable format like a .ipa file for iOS or a .dmg file as you would install on OS X/Mac OS. So I don't think you can simply rename the .zip file to .ipa & install it that way. B/c it needs to be compiled. Especially since Apple doesn't let you sideload apps & forces you to install everything thru the App Store.

A much more technical breakdown of a .ipa file here: https://stefan.arentz.ca/2017/01/27/whats-in-the-firefox-for-ios-ipa/

Going a bit deeper, you could look here to try to learn a bit more about what could be done to install an older Fx for iOS: https://www.reddit.com/r/firefox/comments/8pg9rr/last_firefox_version_compatible_with_ios_935/

It seems to be possible & the last step including iTunes seems to be the easiest solution. Anyway, let me know how it turns out! I'd be very interested to know. :)