If you enroll in design major of Yanbian University, apply for exchange students. You came to Korea in the name of Yan college students. You won't have two diplomas if you study in Korea for half a year to at most one year, because you are a student of Yanda University and only have a diploma from Yanbian University after graduation. An exchange student just lets you experience it and have a look. I don't really want to exchange you with Korean universities. .

Either you give up the admission of Yanbian University and go directly to Korea to study.

I suggest you go directly to extend the university, which is quite good. It takes a year to learn a language directly to Korea. If you want to go to Korea for postgraduate study after graduation. It's not too late to come back then, depending on what you think.