IIT Eligibility

You need to score 70+ in JEE Advanced to get admission in IITs.
If you score more than 100, then you will get upper IITs.
And, a score of 150+ will fetch you admission in you.

Yes, you will definitely get into IIT.
Your available choices are:
IIT, Dhanbad
And other newly opened IITs in past 3 years
https://www.resonance.ac.in/reso/news/jee-advanced-branch-allotment.aspx
Check this branch and IIT college predictor

This year onward, you have to score at least 75% in class 12 marks if not then you have to be placed in top 20 percentile of your bored so if you are in top 20 percentile of your board then you are eligible for IIT exam 2018.
Regards.

Hello Afzal,
If you want to improve your marks, you have to attempt all the papers. If you give one or two papers, it will be not considered by the JEE and your previous year marks will be taken into consideration.

Yes, you can attend exams like above you mentioned but it is compulsory to get 75% in your 12th board and 65% if ST/SC candidate.

Eligibility criteria:
Candidates applying for the admissions should have acquired a first class degree or they should have obtained at least 60 per cent (55 per cent marks for SC/ST) in BE/B.Tech/B.Sc (Engineering)/M.Sc/ MCA/MBBS/M.Pharma/B.Pharma (four year degree)/BDS (4 year degree)/associate membership examinations conducted by recognised professional bodies (like Institution of engineers (India), institute of chemical engineers, aeronautical society of India, institute of electronics and telecommunication engineers, Indian institute of metals, etc.) and recognised as equivalent to BE/ B.Tech degree.

Hi, you must take JEE Mains and Advanced to further qualify for IIT. Check this predictor tool to have an idea about the IITs:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictorv

Hi,
You can take a coaching in an IIT class but you are not eligible to get admission in NITs and IITs as you have only 60% in boards. You should have at least 75% in your board exams to get admission in an NIT or IIT.

Yes, you can. IITs don't have any interest in the college you opted for UG. They only consider your GATE score.

See, if your JEE score is below 70, then there is very less chance for you to score good marks in the next year. (I am talking about the chances, there can be exceptions but exceptions are very less)
Still, if you know that you won't get any decent college this time and have a decent grasp over the basics, then go for dropping.