Why should they give up their nukes? I'd like a rational, logically sound reason they should give up their nuclear research and or any war-heads already developed.
1. North Korea doesn't really need a nuke. That the western allies of South Korea haven't attacked North Korea because it has nukes is overstated. The reason nobody has attacked North Korea yet is because South Koreans don't want to fight a war and endanger their economy. Geographical factors means that South Korea will face significant destruction - missile and artillery fire from NK already can target most regions of SK. And any war with North Korea guarantees the involvement of the Chinese and the Russians too.
2. If we accept the arguments of the west that the nukes are the only reason North Korea has been sanctioned, then giving up nuclear weapons should mean that all economic sanctions on North Korea would be lifted. North Korea already has a reasonably strong conventional military. If the sanctions are lifted, a strong economy + a strong conventional military (along with the military alliance with China and / or Russia) can be enough of a deterrent. Especially if North Korea also behaves as any other responsible nation.
3. Without giving up its nukes, even China and Russia won't allow an independent North Korea, with nukes, to become economically stronger or a democratic country.
4. Right now, the nukes are like an albatross around the neck. Getting rid of them voluntarily can provide immense benefits. NK already knows how to build nuclear weapons. With careful planning, they can resume a nuclear WMD program any time again in the future, if need be.
5. They do not have to give up their nuclear research or civilian nuclear programs.
I mean, it was in a war that they started, so Russia is the attackers. But the attacks are coming back, and the nukes aren't preventing that.
The second problem is that Russia has said what their doctrine is on the use of nukes. They will use them if an invasion cannot be stopped by conventional means, or if an attack has destroyed 20% of their nuclear deterrent. In their attacks, Ukraine is not touching Russia's nuclear weapons (except the odd bomber that is used for conventional attacks on Ukraine).
Now, you could say that was a miscalculation on Russia's part, that they would be better off if Ukraine didn't know what would trigger Russia's nukes, and so Ukraine had to be more cautious. And you could be right. But that ambiguity could come back and bite them later, when someone else doesn't know what their doctrine is, and decides that a first strike is the best way of dealing with the uncertainty.