Sikkim

Hi,
You can opt for IB in class 11th as per your interest. But, it isn't compulsory.
In my opinion, pursuing BBA through distance mode isn't a wise choice. There are good colleges in the country that offer BBA through regular mode with lucrative packages and you should aim for that after your class 12th.
Some of the colleges are: -
Symbiosis International University
Delhi University
Christ University
Mumbai University
SPJMIR Mumbai
IIM Indore - Integrated BBA and MBA
You can start preparing for the entrance exams.

Admission criteria of Sikkim Manipal University for correspondence BBA course is that you should have completed 10+2 in any stream.

You could go for lateral entry, but you should ensure that you block your seat at SMU. Lateral entry is normally granted to students who have a good academic record. You should check with admission authorities if you are eligible for lateral admission and then proceed further.

Dear Vamsi,
Your question is incomplete. You are doing MHM from which University and which semester? Most of the Universities will not entertain lateral entry from MHM to MBA as course contents are quite different. I am sure, SMU will also not allow such a move.

In terms of jobs, there is no good scope. However, you would like to pursue it as a PG program.