Has Russia returned to Communism?
United Russia holds control of the Russian government until 2047, when the Communists finally win an election. They hold the government until the Liberal Democrats win in 2055, losing for mainly the same reason United Russia did (stagnant and weakening economy). In the 2059 elections, the Communists retake the Duma thanks to the economy worsening during the LibDems, but that only lasts until the next election in 2063 when the LibDems win again after the Communists fail to do any better. Things start to get REALLY bad though in the mid-'60s, and this is when people start to really worry about Russia's economy completely collapsing. The Communists take back the Duma in 2067, but it's really too late and despite their best efforts Russia defaults on its loans in 2069, ultimately catapulting the whole world into a decade of recessions and depression.
After all of that United Russia wins the 2071 elections rather easily, both of the opposition parties thoroughly discredited. As of 2080, United Russia is in power.
Why hasn't Russia exerted more influence over Belarus and the 'Stans?
Russia certainly did try to exert more influence, but a number of factors (their shrinking population, worsening economy, growing debt, downsized military, etc.) ultimately shifted their policies. By mid-century, Russia has gone from dominating their neighborhood to trying desperately to stop losing what little influence they have to China, who by 2080 is a dominant (though low-key) force in international politics. If we were to think on very simplistic terms, you could theoretically divide the world into American, European, Chinese, and Indian spheres, with small Russian and Congolese spheres as the outliers (and the Russian sphere by 2080 mostly absorbed by China).
Outside European Russia, Moscow really only has some influence over Belarus, Kazakhstan, and Ukraine, with Ukraine having mostly shifted over to the European sphere. The rest of Central Asia and most of Asian Russia (especially the Far East) is dominated by Beijing or Chinese state-owned corporations.