university change immigration Korea student visa pattern issues Korea part-time work Korea international students student visa korea attendance work rules international student korea immigration international student job rules korea study in Korea student attendance Korea student visa Korea part-time work Korea D-4 work permission D-2 part-time job international student attendance Korea international student Korea Korean university visa student visa transfer Korea student part time work korea visa student visa korea rules international student korea immigration attendance korea student visa document mistake Korea hikorea d10 student visa after graduation d-10 visa korea student visa instability Korea student visa attendance rules Korea student visa korea attendance rules D-2 visa Korea international student visa korea problems job seeking visa korea international student administrative risk Korea international student immigration review Korea student work permit Korea international student visa rejection Korea