What is criteria for C3B to C4 ?

There is no criteria for c3b to c4. That is the most difficult promotion level. You need to have multitude of things in your bucket to prove you deserve c4

Totally depends on your higher management and if there is any requirement. I have seen people with C3B doing manager role for more than 5 to 7 years and still not promoted to C4 whereas during lateral hires if someone has more than 17+ years of experience they are hired on C4.

The criteria for promotion from C3B to C4 in TCS are vague. It depends on manager's recommendation, performance, role availability, and budget. Typically, it takes 4-5 years with consistent high ratings.