Called noted US customer service center and rep provided 8 digit confirmation code to use online check-in. Email received in process included 6 digit confirmation code. 8 digit code works on Asiana web site. 6 digit code works on checkmytrips dot com. Agent indicated inability to change seat but able to change seat online. Process worked via IE 11 and without log on to frequent flyer account. Noted itinerary not associated with frequent flyer account.