Hey there

You have average academics and also your academics is declining so you need to score very good in cat like 99 percentile or above to get iim a,b,c. Usually for these top IIMs you need to score very good but in your case you'll have to be very cautious about your cat percentile if you need these top IIMs.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://bschool.careers360.com/articles/cat-cutoff/amp&ved=2ahUKEwie9rnq37jpAhUEjeYKHfTGCv0QFjAAegQIBRAB&usg=AOvVaw2IdCzY4rRdYaGrBXTO4MVx&ampcf=1

Good luck