There were not two states in Korea at the time, a “North Korea” and a “South Korea”. There is one nation - Korea - and it’s Southern half was occupied by a foreign force. Literally - South Korea was not liberated from Japan at the end of WWII, Japan transferred it’s occupation to the United States.
Depends what’s in season. Where I live: crabapples, blackberries, Japanese Silverberries. There’s probably a ton more, but these are the things I feel comfortable eating whenever I find them at a park etc