Confused.

i think so

all the scenes with Doona in short hair are flashbacks to her college years. the flashbacks are focusing on her messy relationship with Minho (before they broke up) and her fuck buddy funtimes with Wookyung. i think the flashbacks are over by ch80 if not a bit sooner. not positive tho. (too lazy 2 check)

Nope, They're definitely flashbacks

Thank you so much for clarifying!