Dual

No difference in the package. Infact, you may get more than B.Tech Comp Science grads, as a few companies may treat you as Post Graduate. Once you are an engineer or in the process of becoming one. You are free to do any job. Ultimately what differentiates you are the skills you gain and hone over and over again.
Additional Information: Predict engineering colleges you can get on the basis of your JEE Rank: https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor?utm_source=cconnect&utm_medium=CR_JEECP&utm_campaign=8321427.
All the best!

In Kolkata, there are few good MBA colleges:
-Indian Institute of Social Welfare and Business Management, Kolkata
-Future Institute of Engineering and Management, Kolkata
Both the colleges accept MAT scores.

MBA from tier 2 colleges dual program will cost approx.1.5 lc sems.wise
Normally MBA dual program will cost you 5-6 lcs

Yes, you can go through the same after completion of your double degree.

Where do you wish to apply?

I think there will be fifty multiple choice questions each containing 2 marks for a correct response and -0.5 for the wrong answer. 35 number of questions for physics (if physics major) and math, chemistry, Bio each contribute 5 questions I. e, 15 questions from non-major part.