Rodinia:
I'm not particularly fit at the moment due to a not fully healed accident,
Armenia isn't the easiest of countries if you have mobility difficulties. When I visited, I was with my uncle, who was using a walking stick.
Some advice I would have, based on my experience, is to download an app where you can hire a taxi. I had the "gg" app. When I was there, in 2019, it had a facility where you could order a taxi on the app, and pay in cash for the taxi arrived. This was useful as I didnt like the idea of entering my credit card details on the app.
If you are staying in Yerevan, I suggest get a taxi if you wish to visit the Genocide museum (it is not very accessible on foot or by public transport). Then, when you want to return, you can use the Wi-Fi in the museum to summon a taxi via the app.
When we visited the site of Erebuni (where Yerevan began, in the first millennium BC) we discovered that the museum was at the bottom of the hill, and that the remains of the site were on top of the hill. There is a pathway up, but that wasn't practical for us. The staff suggested that we hire a taxi to bring us up the hill (on kind of a service or access road) and pay to have it wait until we wanted to come back down. I had hailed a taxi outside our accommodation to get us to Erebuni but there was no Wi-Fi at this museum to use the taxi app. The staff at the museum kindly phoned for a taxi, and translated as we made a deal with the taxi driver to wait for us at the top.