From the beginnings to the (preliminary?) end of the North Korean missile program

Comparing North Korea's achievements in the field of missiles with the programs of other countries, one gets the impression that North Korea is a nation of rocket scientists. The recent glorious successes appear like a deja vu of the early days of North Korea's missile program in the 1980s and 1990s, when the country managed to present a full missile program out of the blue. But a close look from an engineer's perspective reveals some discrepancies in the common narrative, thus allowing for some surprising insights into the current situation of North Korea's missile threat.