Diploma

Yes, after MBA in HR from top B-schools you can get good job opportunities, highest post varies from organization to organization like head HR, CHRO, Sr. VP HR, HR Lead manager, etc.

To start a business in any field, you require years of expertise and knowledge because setting up a business is a lot more complex as compared to working for some company as an employee. So I would suggest, you should start your business only after having an in-depth practical knowledge of the domai

B.Tech through lateral entry (direct second entry) will be the best option for you or you can even get a job and pursue B.Tech through correspondence, the choice is yours.
All the best.

If you want to make your career in the IT field, then opting for Diploma after completing class 12th will not be a good option, you can pursue B.Sc in IT, B.Tech in IT, BCA, etc. These courses will prove to be more beneficial as compared to Diploma.

You should first complete your graduation and then apply for MBA.