And you seriously believe that if Russia had stated their intention to invade Ukraine that they would have given up their nukes under this 'note'?

All this lawyering-after-the-fact ignores that if what you say is true then Ukraine got screwed over, both by Russia and by the other signatories of that 'note'.

So, the normal response of other parties to such an agreement would be to ensure that all signatories stick to the agreement. Since the only party that conceivably could break it was Russia I'm pretty sure that that was taken into account when the agreement was signed, anything else would be stupendously naive.

The end result of this is that non-proliferation is dead, and that is a net negative for the whole world.