North Korea is not likely to launch a nuclear air strike against Russia. The country has made a lot of threats, but these are aimed at her chief adversaries, the United States and South Korea. North Korea does not have major issues with Russia. But, if North Korea were to launch an attack, it would face massive casualties.
North Korea is NOT going to launch a nuclear air strike against Russia. Kim Jung-Un learned everything he knew from his dad, who learned everything he knew from HIS dad, to carry on this legacy of one persona. That one persona is a God to North Koreans, a literal God. He would not dare start a war he could not win. This is a show of power.
North Korea an especially its dictator feel the need to constantly flex their muscles but they aren't stupid. Russia would make short work of North Korea, and North Korea needs them as an ally. It would be a suicide mission for North Korea to attack Russian, and while they are extreme they aren't nuts.
No strike will be launched against Russia. I believe that Russia is neutral with North Korea, so I don't see any kind of war starting between them. North Korea is not highly powerful unto itself. It is best for the country to control itself. Its leader likes to tease at playing cat and mouse.