It would seem to be opposed to the communist ethos to have airline cabins divided into economy, business, first, etc.
I found this answer from 7 years ago with a quick search by u/kieslowskifan
Yes, they did have a first class, but mostly for international flights. If Aeroflot wanted to compete with western airlines, it should have the same level of service. Sometimes, airplanes from international could be used for domestic flights, and Soviet people could at least see what the first class is, but it was rare, it was an exception.
You can see mentions of that on old Soviet ads (they are in English, and it's no accident): first one and second one.
Also, there was a cover story about Aeroflot in LIFE magazine (26 July, 1968) that mentioned vodka and caviar in the menu. I'm not sure about vodka, but I don't think that caviar was a part of standard menu on domestic flights (although black caviar was much more accessible at that time).
