declaration of sovereignty from the Soviet Union. What the hell kind of revisionist history is this? Russia was the head of the Soviet Union no? The occupied satellites left the Soviet Union in droves and Russia is what's left of it all if my memory serves me correctly.
Memory does not serve you correctly. An analogous situation in the United States would be if all fifty of the states seceded from the federal government. The latter body could still meet in Washington DC, but would be powerless. In 1990, the nation of Russia declared that it was no longer part of the "Soviet Union" which had its seat at Moscow. As Russia was by far the biggest and most important member of that Union, it was a fatal blow. The Soviet Union dissolved its sovereign existence at the end of 1991. Russia is not "what's left" of the Soviet Union; you're confusing the modern nation of Russia with the Russian Empire as it existed before 1917.
You did not know that the USSR's leaders were not always Russian? Stalin was a Georgian after all.
There was never a separate Russian Communist Party. Russians were dominant in the Soviet Union but they resented the drain the empire had on them. Much of the nostalgia for the Soviet Union in present-day Russia is less an affection for Communism than a sense of loss of the country's former superpower status.