>Lots of things get discussed.
Yes, and the contents of those discussions have been released under FOIA.
>This was such a minor topic that Gorbachev didn't even recall it ever having been on agenda.
I have no idea why Gorbachev's memory failed but it's clearly there in the minutes. In many discussions.
Pretending that it never happened is a lie.
>The Soviet Union doesn't exist anymore
Russia is the successor state.
2. The Soviet Union doesn't exist anymore. Even if such assurances had been made, a number (most by now?) of former parts of the Soviet Union have stepped away from it and applied for NATO. Why should Lithuania be eternally bound to an assurance made to the Soviet delegation, which at the time represented Lithuania? Even if all former members of the USSR applied for NATO, should they be denied because of the alleged assurance in the past to an entity that no longer exists?