I think he will try using his nuclear arsenal but most of his missals won't get off the ground. Because of years of improper maintenance, rats chewing on wires and theft of vital parts and copper wire by Russian peasants and Russian oligarchs. Not sure how NATO would react - guess they would have 2 choices blow Russia away or invade it. Cheers and happy weekend!
It depends on just how unstable Putin really is. He doesn't seem to mind sending unprepared, untrained, unqualified men into the fray to get their heads blown off by what appears to be a superior Ukranian armed force. I would like to think that his generals would realize how dangerous using nuclear power would be for all concerned, not just Ukraine, and not obey orders to use nukes.
He might try. I'd hope that the Russian military refuses and sees the order as reason to overthrow him. If Russia uses nukes, she shoots herself in the foot. Ukraine may not have nuclear weapons per se, but they have more than enough radioactive material at Chernobyl to make a very dirty bomb of their own - lacking the destructive power of a true nuclear weapon but a load of HE to disperse it makes for a lot of extremely nasty fallout.
Depends on whether they have a vehicle for launching it at a target deep into Russian territory. They could render Moscow uninhabitable, or make a mess of critical infrastructure.
Nanoose 