CBSE

Hello Ashish,
JEE Mains and JEE Advanced are the only entrance examinations that provide admission into government engineering colleges. While JEE Advanced provides admission into IITs, JEE Mains provide admission into NITs and other government engineering colleges.
I hope this answers your question. If you have any further questions, kindly revert.

Prepare for next year and try harder and think that you have got 2nd Chance to prove.and this are just exams you will get a chance every year. So, don't get upset.

First of all, make your own notes of every chapter. After every chapter, you prepare just solve last 10 years and make a routine for every day. The most important thing finish your syllabus once before December and then in the last three months, solve question papers and then give it to their teachers for checking. Treat Preboard 2 seriously. And one more thing always smile and be fresh as it will reduce stress.

Under the moderation policy, examinees are awarded up to 15 per cent extra marks in certain papers if the questions are deemed to be difficult. In a major decision, the Central Board of Secondary Education (CBSE) has recently scrapped the moderation policy under which grace marks are given to students in exams for difficult questions. It is expected that because of this cut off marks for admission in graduation studies are likely to decrease considerably this year.

Getting a NIT is only possible when you belong to SC or ST but otherwise, it is not possible. But, you can easily get admission in private colleges and can try for government colleges. Or, you can drop for preparation of IIT and can get even IIT college.
Best of luck.

Hard work, self-study and practice should be your 3 mantras to score 95% or above in class 12th.
Good luck!

There are very few colleges offering 100% placement and they include:
IIM, Indore
Nirma University, Ahmadabad
There aren't any more credible institutes for this course. And, anyway it does not matter. If you do integrated BBA and MBA, it will take 5-years and the course fee will be very high and instead if you do 3-years BBA or BMS from a good state university affiliated colleges such as St Xavier's, KJ Somaiya, NM in Mumbai that will cost hardly 1 Lac including everything.Further, you will have more options for MBA later.

Yes, you can take direct admission in JSS.

You can do full-time Diploma in Engineering along with class 12th board in private mode. It will require extra effort and if you have the will to do both simultaneously without impacting your academic performance in both the courses, you may go ahead.