So the USSR is OTL's PRC, and Petrograd was their Tiananmen Square. I think you either stated or implied earlier (certainly by having Alexei Kosygin as General Secretary from 1960-75) that the USSR underwent market reforms at some point. And at various points, we see that this liberalization did not extend to politics.
Come to think of it, we've never gotten a full update on the USSR outside their domination of their Eastern European puppets.
So the Soviet Union has been living under TTL's equivalent of the NEP since the 1920s, with a few minor variations. The political scene is slightly more liberal to the extent that different factions of the Communist Party are allowed to exist (provided they're discreet) and so you do occasionally see competitive elections in some seats. Following elections every five years a Party Conference confirms the Chairman of the Communist Party for another five years. That being said, the commanding heights of the economy are still dominated by state enterprises and held on a tight leash and I wouldn't be too overt about my opposition to the government of the day if I wanted to successfully get a seat in the Supreme Soviet.
One of the reasons why I haven't done a separate update on the Soviets is that their domestic politics has been a little dull since the 1960s: the state is broadly repressive and the people at the top are the same coterie comfortable in their positions. By the late 1980s and early '90s, however, this is leading to divisions, as countries like China and Brazil look like they might overtake the Soviets economically and the cost of holding the CIS down increasingly hard to bear. While it would be wrong to say that people like Gorbachev or Shevarnadze wanted to divest themselves of the empire in Europe, hardliners saw that as a concession that would make the country look weak. Now the Soviets are entering a more repressive, conservative, confrontational period and it remains to be seen what the result of that is.
I take your point about the Soviets therefore acting as a PRC equivalent but, as I was thinking about it, it probably resembles OTL's Putin's presidency but stretched out over decades: a few decades of soft repression partially soothed by a veneer of democracy and economic progress, followed by more hard-edged authoritarianism more recently when that begins to falter. It should be noted that TTL's Soviet Union is in a much better economic position than its OTL equivalent at this time because of the less confrontational geopolitical scene (on that note, TTL's US has a significantly smaller military).
I wonder what is Putin doing right now...
He worked his way up through the KGB and the Soviet-staffed civil service in the CIS (not always distinct services) before resigning to contest (and win) a seat in the Supreme Soviet in the 1990 elections. is still a pretty minor figure at this stage but it more or less thought of as having been supportive of the 1991 coup.
Just after organising a little job in Murmansk?
I don't know what you're implying. The weather is lovely there this time of year.