BCA

Hi,
BCA syllabus varies in various colleges. Generally, following courses are mandatory: Programming languages C+ and or Java, computer hardware basics, data structures DBMS, web technologies, .NET, software engineering, networking, e-commerce, operating system, computer graphics, etc. In addition communication skills, English, mathsn etc. are basic subjects in BCA. Electives can be BIDW, data analytics, artificial intelligence, ERP, etc.

Both the courses are similar with minor differences in electives. You are advised to choose between them based on the reputation of institute where you get admission. Nowadays, it is difficult to find jobs directly if not placed during campus placement. Therefore, quality of institute is more important than nomenclature of degree.

NIT-Silchar, NIT-Agartala, IIT-Guwahati are known institutes for B.Tech in CSE. Other good colleges you can find in Kolkata like Heritage, Techno India, etc.

KIIT is famous for engineering and MBA program. They have lot of collaboration, so you can expect decent placements.
All the best.

No, you can't. You have to leave B.Com and then start BCA from the 1st year.

Both MCA and MBA are equally good career options. If you are technically oriented then go for MCA. If you are not technically oriented and not good at programming then go for MBA. Long term career opportunities and salary after both post graduation degrees are similar. You can select one among them based on the reputation & placement record of the institute.

I would suggest you to aim for MBA after completing BCA because with BCA + MBA IT, you will have dual specialization in technical and management also. MBA is the best career option with large salary scales.

You have to give entrance and pass it. Then counselling

According to me, O level is a certificate course and BCA is a degree. I would suggest you to go with BCA and do part time O level certificate course.