A FlyerTalk Posting Legend
Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 102,617
AFAIK KE participates in the SkyTeam mileage upgrade awards program worldwide. So yes, if there's availability (IIRC it's the same bucket as a low award ticket) you can indeed to use DL miles to upgrade the KE segment between ICN and India to business class if you have purchased a FULL Y fare. I believe the flight needs to have been ticketed on DL stock so that DL can reissue the ticket after confirming the upgrade and pulling your miles.
You cannot upgrade from business class to FC using DL miles.