1st Scenario:
Gorbachev doesn't resign on December 25th, 1991.
(In my opinion, nothing much would have changed if he resigned later, as the Soviet Union was basically non-existent in reality, but in existence by law.) (Newspapers mostly refered to the USSR as the Former Soviet Union since September-Oct 91')
2nd Scenario:
Alizmazhov (Supreme Soviet of the Republics of the USSR) doesn't sign declaration 142-H of the dissolution the Soviet Union, and creation of the CIS)