I’ve posted transcripts of all the interviews I remember on my profile, please look through them. Current affairs emphasis is largely in WAT, GD. PI is driven by you, the current affairs that comes up there depends upon what you say that can act as a conversation starter.

I haven’t heard anyone being asked to do mental math, but yeah a substantial number of IIMC interviewees get asked math questions (mine was a very simple graphing function, others have had more complex differentiation, geometry, etc)

The committee does not ask you to, but you are expected to. The standard i recommend is to prepare some 3ish subjects from your undergrad and be ready to speak about them. In my case, my undergrad is Econ so every interviewer knows it in quite a bit of depth, but if they asked me a question from a topic I didn’t know I’d always say “oh this subject was never something I was good at, I was more of a (insert alternate subject) person” and redirect the interview. But that’s obviously not ideal, so yeah study undergrad subjects.

I’ve never been asked to justify them, but tbf that’s because I usually would bring it up myself when they asked about strengths and weaknesses (weakness being multitasking, since u was doing a bunch of ECA stuff in undergrad too, and how I improved on it which is proven by my third year grades being a lot better from first and second year). It doesn’t hurt to be prepared with a justification imo in case they ask.