CBSE 12th

Hi Nima, you can apply, but universities will check why you took the gap and you have to justify the same very nicely. If you had or have work experience its good for your profile. Also, you must take the SAT and TOEFL to pursue Bachelor's degree in USA. Write to some universities in USA and check with them directly. They are very responsive and will guide you.

Yes, you are eligible for this exam and you can also write this exam. There are many examples of hard work.

I think that B.Sc has an option, where we can take combination of economy and mathematics.

Yes, you can appear for the entrance exam and interview by registering on the http://amity.edu/. You can get admission with that percentage. Best of luck.

Yes, you can get a seat in SRM on the basis of your 12th marks but they will charge you some additional Rs 50k to Rs 60k. So it's better to write the SRMJEE which is an easy exam and you can get good branch in SRM.

Dear,
Based on your query, I would like to suggest the following options:
1. You can go with B.Sc (Hons) in your favourite subject followed by M.Sc.
2. You may think for BCA follows by MCA if interested in the software domain.
3. If you are interested in the Engineering domain, think for B.Tech where your math skill is very much useful.
There are so many wings to study, go ahead based on your interest, skill and industry requirement.
Best wishes.