Dear

Minimum eligibility to appear in IIM admission process is graduation 50 percentage and plus your good cat score . Next admission will be depend on your academic record , gd and pi performance. Your knowledge , positive attitude , Communication skills will be a strong impact for your selection.

All the Best

HI, No.
There is such no criteria for humanities background students to get any sort of relaxation because mostly people from Irrelative streams choose to do MBA.

Selection criteria is simple that is based on CAT percentile (70%) and rest % matters on your GD,PI and WAT rounds. Also this includes your work experience if any.
Your academic performances in past also matters.

Hope this helps.
Good Luck!