Any particular reasons why you want to stay at a no longer supported Firefox 74 version ?

• https://www.mozilla.org/security/known-vulnerabilities/firefox.html

Because the new version got rid of the arrow button in the search bar and I don't like that. I want to be able to pick the web address I want to go to by picking it with the arrow button. I don't need anything else updated.

unchecking "automatically install updates" is only a temporary delay to postpone the inevitable. Firefox will update regardless of what you select in any built-in options. Been like that since Fx 68, although some of the prefs that allowed a user to select never update Firefox were slowly rendered ineffective. I got caught up on that a couple of times; first one 'workaround' stopped working, and then a few versions later a different 'workaround' stopped working.

Note that you can instead press the space bar to open the drop-down list in the current Firefox release.

Hi, make sure that you have also deselected 3-bar menu > Options (General) > Firefox updates > 'Use a background service to install updates.' That way, your PCs UAC should ask before any updates are allowed.

In addition, be aware that some antivirus programs (Avast is one) contain a 'Software Updater' - or similar, which unless disabled, will automatically update any out of date programs on your machine - probably including Firefox, so you might want to check out that possibility.