Computers & IT (Non-Engg)

No, not compulsory. You have other options after BCA like MCM(Masters in Comp Management), Masters Degree in Information, MBA, MSc IT, PGD in CA(Comp Applications), PGPCS, PGDM, Programme in Information Security Management. Decide well !!

SAP is an Enterprise Resource Application (ERP) application software package. ERP applications integrate all of the organization's principal processes. ERP provides a cross-functional, process view of the entire organization. SAP is a leading player in ERP market. SAP certification in business processes such as Sales and Distribution, Production and Material Management, Finance and Account etc will add value to you and provided competitive advantage to you vis a viz basics degree holders of your field.

both the fields are good.it depends upon your choice that what you wanted to do. Feel free to revert.
All the best!!!

These are the colleges present for BCA. Just check individually which all take students without maths in +2.
http://entrance-exam.net/bca-colleges-in-kolkata/

Make a list of colleges and just check which all colleges take students without maths.

you can do a professional course for robotics

last week of may
probably after your board exam results

NIT is best in nagour

I am not really sure about the market outlook but as far as career is concerned I can share a few things that I know.
For making a career into SAP FI you require at least 2 years of domain experience so that your placement happens smoothly after the certification exam.
Your career starts as a SAP FI fresher and then you go on to become a Consultant within 6 months to 2 years, depending on your performance. You are then put on core teams and allocated clients, for which travelling and relocation becomes a must in this kind of a job

If you are interested in Science field, then proceed with BSc. If you are highly interested in Computer science then go ahead with BCA. Both the fields have equal job opportunities.