Dual

This is not same as always and changes according to the requirement every year. Sometimes you might get this in first category or sometimes it can be in third as well. But this time it seems you can get in second as the seats have not been fixed by VIT.

In my opinion, dual degree courses in NITs are not too bad, if your rank is not too good. But, if your rank is good , go for B.Tech and after B.Tech , clear GATE exam and opt IIT, if you still have to do M.Tech.

I would encourage you to get your NCERTs and RS Agarwal sorted out for reasoning and competitive exam. For Verbal Ability, refer to Wren & Martin or some primer like McGraw Hill or Pearson. Solve a lot of mock tests and practice a lot of questions.
For the interview, prepare well about your background and also about the subjects in which you have high marks. The panelists are mainly interested in screening your confidence. You must definitely try to give some mock interviews.

No, for the MBA degree you required graduation level qualifications for getting admission in the college, so as per that, only you can consider yourself every time, which will give you best boost.

Hello,
In Welingkar PGDM core, they offer you Major and Minor specialization.
Click on the below link to know more:
http://www.welingkar.org/Home/home_flash.asp

If college will fund your stipend for your Ph.D, it would be a better option. If not, it will take a long time to get out of this course and to find jobs either in the education field or in any other field. No company will recruit Ph.D graduates directly at the initial level because of the fact that they need to pay a higher amount for the same job that would be done by a UG student. Please select carefully. Only if they provide stipend during your Ph.D then opt for the same.
All the very best.

You can refer to the link below to get the full details of the fee structure:
http://www.vit.ac.in/admissions/pg/feeStructure