Masters

If you want to be a teacher, you have to do B.Ed because as per the rules it's become compulsory for teacher to have degree of B.Ed. So after doing PG course, you still have to do B.Ed. So, better option for you is that you can be a assistant professor in any college after having PG degree and than cleaning UGC NET. So, you have to option either you do only B.Ed and became teacher in school. Or, you can do PG course than clear UGC NET and became lecturer in college.

It is a regular course. Seats are around 40-45. One have to qualify written exam.

No, there is no PG diploma in travel and tourism in Jamia Milia Islamia University.

First of all, congratulations for your graduation.
Yes, you can go ahead.

Yes, you can definitely do Masters in Environmental Science after completing your Aviation degree. Best of luck for your future and if there's any query, feel free to ask.

IB is International Business and HRD is Human Resource and Development. Both are different according to specialisation. Choosing which one to go for totally depends upon your field of interest. MBA degree is more valuable compared to M.Com. So, I will suggest you to go for MBA.