India

Yes, you can do it. It depends on your IELTS score and your graduation marks.

You can do MS in maths, eligibility is 50% in the degree. As for now, admission are closed but some private universities have seats left, you can apply there.

All the subjects needs to be cleared to join any course in future.

You have to just apply for the B-School in Maharastra and you can take admission on the management seat.

If you intend to migrate to Canada, then it makes sense to pursue PhD there. If you intend to return to India and work here then MBA in India is more relevant as the campus placement process will be an added advantage.
Job opportunities are a function of multiple factors and a good candidate is always able to seek employment.

Dear Khanisk,
If you are interested in aerospace, please join IIT or NIT or go abroad for studies. Most of the best is doing aerospace engineering in abroad like USA, UK, etc. Aircraft industry in India is not developed so there is limited chance of getting job in India.

IGNOU is the best option for MBA-HR by distance learning. It is a central university which is well recognised with excellent course material.

Focus only on your CAT %tile. Atleast above 97 because 12th percentage weight-age is very low.