B.A

First, you should decide what you like to do and where you have an interest. When you will find your interest then only you will get the job satisfaction. If you have an interest in the technical field, you can choose computers course, if you have an interest in traveling, you can choose tourism and hospitality course, etc. So first, you find out your field of interest.

For doing B.Ed, one must secure a minimum of 50% and for other than general category, a minimum of 45% is required.

Hi Jasbeer,
Please first check the entry requirements, many post-secondary certificates are below Bachelor's degree. In that case, chances of admission or even visa are low. You can check your concerned college website for details. Visa is not a guarantee if you are applying to a course for which you are overqualified. Otherwise, it will also depend on your overall application package.

Please refer to the link provided below for the list of colleges which offer BA. Maths (Hons) is mostly synonymous with B.Sc and BA (Hons) in Maths is rare as BA is mostly Bachelor of Arts.
Kindly visit this link to know about the colleges in India offering BA:
https://www.shiksha.com/humanities-social-sciences/colleges/b-a-colleges-india

Yes, he is eligible subjected to the following conditions:-
1. Score more than 50% marks in graduation
2. Score more than 95 percentile in the CAT(since he is into Arts ,he will have to put in special efforts to prepare himself for the CAT curriculum).

Yes, you can apply for BA journalism after completing 12th from commerce stream. The eligibility criteria for this course is 10+2 pass.