B.Com

You can do BBA by studying at home.

For B.Com entrance test you can refer NCERT along with general English and aptitude.

Yes, of course, it will remain valid, you can change your class 10th board.

Yes, you are eligible of giving IBPS exam. You just need to complete your graduation from any education background.

For appearing in CTET you need to have done Diploma in Elementary Education, Bachelor of Elementary Education (BElEd), or Bachelor of Education (B.Ed).

It is not possible, as you have cleared according to the criteria of Sol, so there is no chances of reappear.

You can do CA CS CFA. ICWA and Law kind of Professional Courses.
Prepare for Competitive Exams for Banks, Insurance, Income Tax Officer, Railway Recruitment Board, UPSC and State Public Service Commission.

Go for BBA and then MBA. This will provide you a great hike in your career, as it will get you an impressive profile and package in an organization.

Go through internet, newspapers, try to read all kind of books, current affairs and magazines.Try to interact with intellectual people, do group discussions with your friends.

Yes, law is a good option to do after B.Com. Not only B.Com, but any graduation, since it is a field different from all and is gaining momentum. There are a lot of career options after LL.B. Such as:
Litigation
Judiciary
Own Firm
Corporate
There is no prerequisite condition to do LLM to enter into corporate, you can enter into the corporate world with your LLB Degree as well.