For both dates:

https://en.wikipedia.org/wiki/Declaration_of_State_Sovereignty_of_the_Russian_Soviet_Federative_Socialist_Republic

The Declaration was adopted by the First Congress of People's Deputies of the Russian SFSR on 12 June 1990. It proclaimed the sovereignty of the Russian SFSR and the intention to establish a democratic constitutional state within a liberalized Soviet Union.

https://en.wikipedia.org/wiki/Belovezha_Accords

The main obligations of the parties to the Agreement, ratified by all former Soviet republics except Estonia, Latvia and Lithuania, includes the following:

1. The end of the existence of the USSR, with the "setting up of lawfully constituted democratic… independent states… on the basis of mutual recognition of and respect for State sovereignty".

Clear enough for you? The CIS is the successor to the USSR, not Russia.