hi,

see IITs btech admission is based on jee advance score. however you must get the qualifying marks in jee main exam to become eligible for jee advance exam. how jee main and jee advance exams syllabus is based on physics, chemistry and mathematics and you must have three subjects mandatory in 12th course, if your dreams to become an Engineer. however in optional subject you may take biology/ computer science/ statistics etc. however it does not matter whether you have studied computer related subjects or not. however as for the engineering / btech courses syllabus it would be best for your future studies if you take statistics/ computer science in 12th course, would beneficial for you in near future.

hope it would help.