The behind the scenes ship tour will include several areas with bulkhead doors that require you to step up and over the threshold - several inches. They are taking you to employee only areas in lower decks that are not built for wheelchairs or scooters like the main passenger floors.
I used tours by locals when my mother was no longer able to climb the couple of steps into the buses. I do not expect old port cities like you listed to be very wheelchair friendly. It just isn’t a thing like the US ADA laws.