Waterfox may be based upon the Firefox ESR version, but its not supported by Mozilla Support.
Try: https://www.waterfox.net/ for help with Waterfox.

As far as "verification", authentication codes, password reset, and such do those involve a Firefox Sync account?

Hello,

yes it does involve the firefox account.

Kind ergards

With Firefox Sync the latest Password is needed to connect back to your Sync account. When the Firefox Account for Sync is reset all the data is wiped from the account. The data which is sent to the Sync server is encrypted via the Password being used at that time, a new Password wouldn't decrypt that data so the data is worthless and is wiped. Plus, that feature allows the user to remove corrupt data from their Sync account; it is a sorely needed maintenance feature that was lacking years ago. Personally I ended up with 5 different Sync accounts over time because I was suffering from corruption, and needed to start with a new, fresh Sync account in those days to continue using Sync. BTW, I was a volunteer "tester" of Weave, which later became Sync when it became a standard feature in Firefox, when it was available as an add-on for users to follow and to contribute to the Alpha and Beta stages of development. But I gotta level with you, I ain't happy with the end product and don't use it other than to observe how it works between 2 Firefox Profiles on the same PC. And that is what Sync does is to synchronize user data from the Profile, whether it is on one device or multiple different devices. I just don't have the need for owning multiple devices as a retiree on a limited income and no longer have outside employment as I did before the Great Recession which killed the income for part-time jobs. Early version of the "gig economy", IMO. Crap wages and no benefits, and when business is slow a person is sent home mid-shift.