CS Examination

If you want do an integrated course again, then go for one of the nationals by taking CLAT or AILET.
And for a 3-year LLB thing, you can join Faculty of Law, DU, BHU, AMU, JMI and other state universities.
Moreover, you can do CS simultaneously.

No idea about CS, so can't comment. But for MBA, yes, the academic scores especially the graduation marks do matter as a lot of top B-Schools give significant weightage to them. During the interviews, one can be questioned about his graduation marks (if low). Also, once getting admitted into a particular B-School, there are companies who consider the graduation marks seriously while recruiting for summer and/or final placements.

The main difference between CA CS studies is that in CS, you are going to learn more about company law and in CA, you are going to learn more about accounting and taxation.

You may refer to the following link to get an idea about salaries of company secretary in India:
http://www.payscale.com/research/IN/Job=Corporate_Secretary/Salary

MBA after B.Com is a good option because it has good job opportunities provided you do MBA from a top colleges. Otherwise B.Com+CS is also a good option.

If you are interested in the business field then opt for BBA. It has a vast scope.

Hi
After bachelor's, you have 2 levels to clear:
Executive and professional. The duration is not specified as such and it depends on your registration. For more information, read here:
https://www.icsi.edu/WebModules/AboutUs/Courses/CS_Course.htm

If you are a Company Secretary qualified, then you have skills to be part of Corporate leadership on fast path then why do you want to de-accelerate your career by doing MBA from a normal local BSchool. You must aim for admission in top B-School only after CS.

Dear,
CFP or CFA certification not only gives you help to get the job but give you knowledge and skills in respect of financial planning, portfolio management, understanding of market.
So, in campus placement, opportunities not only depend on this certificate but your academic record, internship, research, your positive attitude and career goals.
All the best