Full Time B.Com

No, it is not compulsory.

For private or distance, you may directly enroll with the institute of distance and open learning. Visit mu.ac.in and for regular, there are many check it on the university website.

If you are a working professional, MBA will help to perform your work in well organized and planned manner, plus it can be helpful in getting you promotion.
MBA is not only about business, but it helps you in overall development of once personality and ability.

The majority of syllabus of B.Com (P) and B.Com (Hons.) is same. B.Com (P) gives an overview of the various subjects where the same course in honors has more depth and content. In B.Com (P) you cannot specialise but in honors degree student can specialize. B.Com (Hons.) is now a de-facto a standard accepted degree for jobs. Cut off for B.Com (Hons.) is higher in comparison to B.Com (Pass). If you can get admission in B.Com (Hons.) then it will be a better option in comparison to B.Com (Pass).

Dear,
You can opt for B.Com (Hons) or finance out of the available 4 options due to its vast course module and knowledge.
All the best.

No, it won't be tough as the syllabus correlates.

You can get a job as a financial analyst or financial planner. As you have done CS, so you can get an option in finance ethics in which a cross check of entries has to be done. Otherwise, you can get a job in the finance department.

No, it is impossible to complete both B.Com and MBA within 3 years under Indian education system. You have to complete 3 years of graduation and then you have to go for 2-year MBA.