It doesn’t seem likely to me, I haven’t really heard that opinion from foreign policy experts on Hoover or the Economist etc. Of course anything is possible but it’s hard to see what would be gained.
RU has said that they will use nuclear weapons if their territory is threatened and UA and RU have territorial disputes.
Personally I don't see a situation in which UA is able to take Crimea and RU doesn't launch a tactical nuke. Putin isn't going to allow Crimea to be taken, and I honestly suspect he'd rather risk his life than live with the shame of such a defeat.
But this assumes that UA would try to retake Crimea and that's something that will only happen if UA manages to push back RU. And while Zelensky has suggested he wishes to liberate Crimea, whether he will or not probably depends on US support. So there are at least a few conditionals here, but I personally don't think Putin launching a nuke is that unlikely in the event of an embarrassing defeat where contested territory is taken from them.
Yabbut the Russian government considers half of Ukraine to be Russian territory, including a good chunk of Donbas that they don't even occupy.
I don't think they'll try to use tactical nukes, even if Putin is on the rocks politically; it's really hard to occupy territory that's been devastated by a nuke, and you need the right equipment. The Russian forces are notoriously ill-equipped.
Also, I suspect the Russians doubt whether their tactical nukes actually work. These devices need constant maintenance, and critically they need fresh tritium. I doubt that manufacturing and distributing tritium is higher on the MoD's agenda than delivering artillery shells to the frontline.
What Russia says is worthless. Not sure what makes you serve as their personal rebroadcasting device.
Ukraine already "occupies" territory which is part of the Russian Federation according to its constitution.
Also, I don't believe Russia ever said this. Russia has a nuclear doctrine, which basically says that Russia can use nukes if the existence of the Russian state is threatened. (and of course to retaliate against a nuclear strike)