Hi!
I'm also an international applicant from India
Did you do CBSE?
I assume 10th and 12th class are the only ones that the universities would care about, since 9th and 11th are not marked by board but they are internal school exams. Hence your 11th grade marks should not matter, and I don't think you would declare this anyway on your application on UCAS.
Oxford accepts CBSE and as far as I'm aware you need the Indian equivalent of A*AA - which as per their website for CBSE is: A1 / A1 /A1 /A2 /A2. As per Oxford, A1 = >91% , and A2 = 81-90% . So you will need to score >91% in three subjects.
From what I know anecdotally, Imperial did not accept CBSE as of many years ago.
I am unfortunately not aware if this is the current situation, and you will have to email Imperial to know the same. Same goes for BSMS.
Remember for Oxford you will
literally need the highest BMAT scores you can get, because I assume you would be shortlisted purely on the basis of your BMAT score and Oxford's international competition is very intense indeed, with a near to 1% offer rate. Imperial also have a high cutoff (I think it was >13 for S1 and S2 combined this year). They both would care more about your BMAT to shortlist you than your experiences. But it's nice that you are involved in such a wide range of activities, and that you have some form of WEx.BSMS on the other hand is less BMAT heavy than the two, and
recommends two weeks of work experience I believe.
No, you do not need to sit any additional exam apart from the BMAT (or UCAT if you choose a UCAT uni) and IELTS. For IELTS, most will require you to have a 7 to 7.5 overall. You
might have to take the NEET now if you plan to work in India after your graduation,
but this is in no way looked at or even part of your application. Your university will most likely not even know what NEET is, it's more of a requirement to work in India.