I heard Ananya addressing Sid as "Kesur" a few times yesterday which I thought was really weird. I am sure they are going to use that in some way in the coming episodes.
Yeah it is "K Sir" short for Khurana Sir. So if she addresses Sid as "K Sir" in front of Roshni/Ragini then she won't be able to put the two together as quickly.
Anupamaa
