Mechanical Engineering

Hi,
Yes, you can. Any one can apply for NIFT after completing 10+2 with 55% marks.

Hello,
It's nice to know that you have completed your Mechanical Engineering recently. Now what should do? You have two choices. Firstly go for PG in a suitable field in engineering. Alternatively go for MBA. Former will take you on the path of becoming a technocrat while later will take you on the path of managing. It actually depends on one's passion and skill sets acquired. Both paths require different sets. And then there is passion! I would advise you to follow path of your passion.

Hi,
Well, there is no specific book for DTU LEET preparation, but there are plenty of books for other LEET exams, the one most popular is by author Vaneet & Gurmeet. Here is the reference for that book LEET (Lateral Engineering Entrance Exam) Objective Type.
https://www.amazon.in/dp/9351920453/ref=cm_sw_r_cp_apa_i_VphwAb6AJP8VQ

I think you should take a choice on the basis of your interest in the field rather looking for the placements, because your interest in the field will give you the placement.