Stalin dies on 12 April of '45? The Soviets still finish off Berlin (they were already in the City on 4/12).
No they werent. The battle for Berlin started on april 16 and it took 1 week to reach Berlin. Zjukov might not have pushed so much at Zeelow heights if Stalin were around so a few thousand soviets live a bit longer
If Soviet military is needed on the homefront to keep Russia from going unstable, is there any chance that any countries in Eastern Europe get their democratic elections?
In OTL different Eastern European countries had different experiences in the immediate aftermath of 1945. Czechoslovakia had fairly free elections which the Communists legitimately won, or at least emerged as the largest party.
Plainly Poland was different. I am not sure about other Eastern European states but I think it is worth remembering that most had been Nazi allies.
Someone said that the USSR might not have declared war on Japan on August 8. I disagree. I believe that was part of the Yalta deal and a Soviet leadership would stick to it so they can get the rest of that arrangment.