CBSE 12th

You can do Diploma in this field, but I would suggest you compare it with BBA in aviation management which is a highly professional course and then decide what to do.
Regards.

There are various good courses which you can do after class 12th if you opted for science stream. You can become a doctor, teacher, engineer, analyst or researcher.

If you really want to get a good college for aviation, 50% marks will not help you to get into a good government college so search for universities like GGSIPU which conduct their own entrance exam and try achieving a good rank there so that you get a good college.

Yes, you can get the admission.

The minimum fee for CPL starts from 20 Lakhs.
Every academy has different fees.

Engineering and J&M are very different from each other. While you have to exert a lot more for engineering, it will be more fruitful. But if you actually want to do Journalism and Mass Communication then you should go for the course you really want to pursue.

For PG Diploma in industrial safety management you ought to complete graduation from a recognized university.
The PG Diploma full time course is of 1 year. You can get into 1 year Diploma in fire and safety.

Here are the career prospects after bio chemistry:
You should do M.Sc biochemistry. You can do M.Sc chemistry if you have chemistry as a core subject in all 3 years of B.Sc. 12th subjects don't matter much.

Yes, you can do mass communications even after doing B.A. English. The best universities are:
Delhi University, Delhi
Jamia Millia Islamia,Jawaharlal Nehru University, Lovely Professional University Jalandhar
University of Pune, Dr. Bhim Rao Ambedkar University, Agra
Banaras Hindu University
Anna University
Christ University, Savitribai Phule University
The Maharaj Sayaji Rao University,Jadavpur University,University of Hyderabad

No, you can't. JEE paper 2 can be taken only by those candidates who have physics, chemistry, mathematics as their subjects, along with meeting other eligibility criteria.