Teaching & Education

Yes, you can apply for B.Ed.

One thing is that you can't get a permanent lectureship with only B.Tech in your hand. As per the new AICTE regulations, there are no lecture posts in engineering colleges anymore. The name of the first lectureship post is Assistant Professor. So you do need a PG (in your case M.Tech.) to enter into the lectureship. You do get lectureship as a guest in some self-financing engineering colleges or in poly techniques.
If you take your PhD, then you can start your career as an Associate Professor (Professor if there is vacancy).

Sorry, now you cannot take admission through NIOS.
Refer the link for details: http://www.nios.ac.in/student-information-section/admission-procedure.aspx#proc

You need to pursue B.Ed after completing UG.

No, you cannot. BA and B.Ed are compulsory for TGT.

If you are doing graduation degree from a recognised university you are eligible to seek admission in PG degrees such as MCA, MBA, MSW, MMC, etc. subject to meeting other eligibility criteria.

All the teachers are partly dependable. I speak from my personal experience. If the scripts are given to a different teacher, you may be disappointed. I suggest that you should do your best and then depend on your teacher.

If you are getting government college in MDU then go for it. Otherwise, IIMT is a better option.