Frame 2019 to 2020 upgrade questions

Hi

The company I work with has several FM subscriptions; we're all using FM 2019 (15.05.838) because (since updating to Win 11) we've been unable to run the more recent updates. Next week a new user is joining and will need to install a new copy of FrameMaker. So several questions which I had been deferring because they were not urgent have now become more pressing.

Because our maker.ini etc are under source control, we all need to be on the same FM version; install together, and update together.

What might be the simplest option: can I install a brand new copy of FM 2020 myself, run it simultaneously with my current FM 2019 on my laptop with my single subscription while I identify any changes/improvements and document them for the rest of the team, and then we can all jump to FM2020 next week?

The more complicated option is expecting the new user to find the 15.05.838 installer and run it on her laptop, because I expect that she would have exactly the same issue with completing the installation as we had when we tried to update past 2019 update 5.

Just to make things worse although I manage the use of Frame I don't manage the subscriptions. I can check my Adobe account and all I can see there is that I have a current subscription, which doesn't seem to be keyed to a single version. But I'm, just guessing here.

Can somebody point me in the right direction, & thanks very much?

cheers

T