Two things in life I hate and Updating mission critical software is both of them

Recently had to update Quicken 2017 Home and Business to 2020 Subscription even though 2017 was "finally:" working flawlessly. It was expiring. The upgrade went OK, but immediately and not surprisingly found issues and numerous undocumented (at least for me and my searches) changes all in Bills and Reminders. No problems in other parts of Quicken.
A thread here on Community suggested that the password for a Data File is removed before Updating. I wanted to be sure that was required so started a thread. Found that removing password was not necessary and that thread bloomed into all my issues with the Update / Upgrade. I have closed that thread and thought a fresh one showing what I have found could be beneficial here. Old thread was:
https://community.quicken.com/discussion/7874341/data-file-password-during-upgrade/p1