IIT

First of all, you have to take admission in B.Tech through lateral entry. After that, you have to clear GATE with good score after B.Tech after that, you can get M.Tech in IIT through GATE.

There is no job for IIT after 10th. You can get only very cheap job. For a better job, you should complete graduation.

Apply for JEE Mains but currently, there is no chance for JEE main because its application submission last date completed and papers also going on. JEE Mains and JEE Advanced, the only way to get admission in IIT college.

You can take admission in any private college for B.Tech. Stay aware & updated about state level counseling in your state, on the basis of your board marks you will get your seat there.

You cannot get admission in IIT on the basis of JEE Mains, but clearing it is an eligibility criterion for taking JEE Advanced which is the exam for getting into IIT.
For JEE Mains, you need a minimum of 100 marks to stand a chance, but you are still not in the safe zone.
As every year the cut-off revolves around 100.
For Advanced, the max. rank to get IIT-Kanpur or Kharagpur is 30K to 35K but then too you have to compromise with the branch.

I don't know about the reservations, but for admission in a good NIT, you don't have to wait for the JEE Advanced score, you can get admission to the college by getting at least 250 marks in the JEE Mains exam.

See there is nothing called best coaching it is you who makes the difference join any coaching which is near to your home if you work hard and smart you will soon realize once your concepts are clear you just need practice to clear JEE with flying colors just note this you will have to put a great effort as there's a huge competition. All the best.

Eligibility criteria:
IIT JAM 2018 Subject-wise cut-off is mentioned below. Please check, if you made the cut from the marks mentioned below. In Physics, qualifying marks for general category are 19.51 while for SC/ ST/ PWD, it is 9.76. For Physics Paper/
In Chemistry, qualifying marks for General Category students are 14.79 and 7.39 for SC/ST/PWD. For Chemistry Paper of IIT JAM 2018. In Mathematics, qualifying marks for General Category are 23.35 and 11.68 for SC/ST/PWD. Based on IIT JAM Result 2018, candidates will be admitted to institutes if they fall in above eligibility then you are eligible.
All the best.

Best IIT coaching is self-study. There are many coaching classes such as FIIT-JEE, Akash and you can also opt for individual tutors for each subject. Explore by asking you seniors. Consult you school teacher/friends. Individual tutors will have in-depth knowledge of the subject. All the very best for you exams.

For IIT, it is 75% and is the easiest part of it. If you want to join IIT, you need to crack JEE Mains and JEE Advanced as a good rank in advanced can get you a seat in IIT. Though you must be eligible for NIT if you get your expected marks, but to get a seat there, you need to perform well in JEE Mains.
All the best.