If ,For any reason, Ronald Reagan was not become President of United States in 1981, The USSR would fall same?
Without Reagan and his politics we would have Gorbaciov,the fall of Berlin Wall,the end of Soviet Union?
Arguably, Reagan kept the cold war going single handedly. The truth of the Soviet Union was that the Politburo was uniformly old sick men who had come to power through WWII. During Reagan's term, they kept dying in office - Breznev, Andropov, Chernenko. Andropov in particular, was convinced that the US was going to launch a sneak attack and start WWIII any day now. Reagan's aggressive posture and military build up persuaded them that they had to hold onto a hard line, and that meant holding down moderates.
Gorbachev basically came to power 20 or 30 years younger than his predecessors, and out of the Agriculture ministry. It's pretty clear that under the circumstances, this guy with his glasnost and perestroika was the last guy that they'd have wanted to pick. But they were going fast.
So I'd say that there's a pretty reasonable argument to suggest that without Reagan, Gorbachev may have come to power faster, and that the Soviet Union might well have dissolved earlier.
Certainly the key factors underlying the dissolution of the soviet union - their deeply rooted economic problems and the aging out of the old guard, had nothing to do with Reagan.