Answer updated to "Czechia". Once the Democratic People's Republic of Korea shows any sign of being democratic, or of the people, we'll consider DPRK. At least it's a republic, in the narrowest sense of the word.
I think keeping to conversational names - ie the names almost always used in conversation - is best. No-one says "I'm visiting Republic of Korea" and they don't say they're visiting ROK either. Virtually everyone would say they're visiting South Korea.
You know it's going to be a bad run when you start: Canada, United States, Guatemala... I definitely should never be a stenographer. Regardless of my inability, I love all these speed typing quizzes of yours!