Class 11

Hello Chitrangi,
Presently, you are in 11th and is desirous of appearing in different exams. But which exams? Towards Engineering or medicine? What subjects you have chosen at present? For medical it's only NEET. For engineering, it could be JEE or CET of your state and of some private university offering degree in engineering. Just read newspapers and you will come to know.

From science, you could only switch to arts. There is no option of shifting to commerce.

Your 11th marksheet isn't important. However, you can ask your school principal to give you a certificate that says that you have passed 11th standard.

HI Tanmay Kapil,
Yes, absolutely. Complete your 11th and 12th with high academic percentile and get involved in high end extracurricular activities too. If you want to study in USA take the SAT or ACT during your 11th or 12th. You must also take the TOEFL or IELTS. Decide where to study and what to study first, accordingly you must check the requirements and prepare.

No. You have to pass class 12 too.

You need to enter class 12th marks for the radio application.

You need to give CAT entrance exam to get a BBA college.

The exam may be the same but the colleges you will get on the basis of the marks will be different.