CBSE 12th

Hello Manish,
After 12th, doors to the whole world of different streams are opened to you. You should do B Com. Then after passing there are literally hundreds of different Specializations that you can think of.
Best wishes

If you want to join a government sector, you have to prepare for SSC, bank PO, NDA, etc.

BBA is open to students of all disciplines. As a Humanities student, you will face no problem in doing BBA. You may feels Managerial Maths and Commerce new but if you attend classes and practice, you will able to get good grades.

Well, there are most of peoples who are not from Biology background, but they apply for compounder. You should also try for it.

Hello Jaymin,
There are plenty of Institutions in India and must be in your town also who take different courses from one month to one year duration. You have a look at these and then select the one that you like best.

Hello Ammar,
It's actually very simple. Set time table for study everyday. Cover every subject every day. Assign time for exercise and Pranayam. Assign time for leisure activity. After few months, take mock exam every week and get answersheets analysed by good teacher.
Best wishes

Hello Allen,
There is no upper age limit if you are seeking knowledge. You can always complete your graduation in one if the subjects offered by distance education Universities like IGNOU or YCMOU.C
Best wishes

Hello Vikram,
Why not? Admissions to IIM, Ahmedabad are fundamentally based on marks obtained in CAT conducted by one of the IIM's every year. If you manage to come within top 50 you are sure to get admission.

Hello Shirish,
It's indeed very creditable that you are thinking of doing graduation after do many years. Keep it up. You have two options. Join college physically and do graduation. Else take up one of the courses offered by distance learning Universities like IGNOU or YCMOU etc.