Engineering

No, NCERT is enough if you are clear with the concepts. PESSAT is easy as compare to JEE. So, read NCERT thoroughly and refer previous year questions also.

MIT have its own entrance to join their courses. If you have JEE Score, it will add value to your application over there.

I suggest you to go with Amrita, PES or PSG. All these campus are highly reputed and are giving placement with good package in reputed firms.

Yes, of course, the campus has enough reputation and lot of students are getting placed from the campus in reputed firms. Go ahead.

There are lot of institutions which offer GATE coaching. After your B.Tech or B.E its better to go for coaching in a reputed institution and get through with the GATE exam. Its little tough so need time for preparation.

Sorry dear, as your score is too less, you cannot get any nit college with ECE or CSE branch. You may get any other branch. First, try out your counselling process of JEE Mains. And try out Shiksha JEE college predictor for other good colleges according to your score.

Yes. You can give JEE again in 2019. Its actually good so that you can get score and better college. Try for 2nd attempt in 2019. If you want to check colleges based on your current rank use below link:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor?utm_source=connect&utm_medium

Well ! As per your marks, you can get any good private college because It is tough to get any NIT or IIIT for you. So, go and try for some private universities and colleges like:
LMNIT, JECRC (College), Nirma University, DHIRUBHAI Ambani Inst. of Technology, etc. According to your score, you may get

Hello Das,
No, for getting admission in any undergraduate courses, you will have to produce your 12th passing certificate otherwise you will not get admission. Best wishes.