Would a nation want to nuke territory it wants to conquest. I am not a brilliant DEI general but it seems that it would be a bad idea and nukes are only really useful as a deterrent. Not for capturing territory.
Generally correct - this is a Muscowite bluff to nuke parts of Ukraine.
But note “generally” - this war was started as a case of hubris by an old man - Putin. If he gets frustrated with no win, he MAY decide to go with a bang