None of that happened while Kim Jong Un is in power. He's not his father, and he's shown unprecedented willingness to cooperate with the west. He's talking about visiting Washington. I think it's for real this time, and I wonder how long people like you will foam at the mouth before finally realizing you are wrong.
That's what happens when the you're the supreme leader of the DPRK and the Chinese decide that NK has outlived its usefulness as a regional counterbalance. The smack upside the head from Beijing is the source of that "unprecedented willingness", the fact that Moon Jae-in and Trump recognized that opportunity is a credit to both of 'em, let's just hope the opportunity isn't squandered.
Yes, China is likely a large part of why Kim is cooperating. I mentioned that in another thread. That makes me even more sure it's serious this time.
IMHO China is probably the only "part", the North Koreans are nearly entirely economically dependent on the Chinese, if a lasting peace is achieved on a denuclearized Korean Peninsula then the need for a U.S. Military presence in South Korea will evaporate and open the way for a Chinese-South Korean economic alignment, thus vastly diminishing U.S. influence in Asia.
Make no mistake, if this all works out, China stands to benefit the most from it.