Hello

You want to study bachelors in computer science then yoiu have to do class 12th with good marks and prepare side by side for JEE Mains or state entrance CET , your target should be high since if you would prepare for JEE Mains and crack it with good rank then you can easily score in other exams too.

There are many colleges, govt colleges has less fee and provide good placements and opportunities the private college have high fees any only few are woth for that fee.

Hope it helps.