I couldn't find details on any such agreement, I'd be curious to see it. The only treaty signed between the two countries from that period I could find was the leasing to Russia of the Sevastopol naval base in exchange for preferential gas prices to Ukraine.
Still, to be very clear, I don't mean in any way to claim that Russia has any justification whatsoever for invading Ukraine and stealing their land, with or without some treaty.
Still, to be very clear, I don't mean in any way to claim that Russia has any justification whatsoever for invading Ukraine and stealing their land, with or without some treaty.