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