IIT Scores

No, of course not. To crack JEE, you need Arihant and Balaji (organic chemistry). TMH too as they have lots of questions to help you build your base as well as advanced level.

JEE Mains is for those candidates who wish to get into BE or B.Tech courses in the National Institutes of Technology (NITs), Indian Institutes of Information Technology (IIITs), other Centrally Funded Technical Institutes (CFTIs) and engineering colleges of the participating states.
The JEE Mains is also the eligibility test that allows students to give the JEE Advanced exam which eventually leads to admission in either the IITs or the Indian School of Mines (ISM).

Being an SC candidate, you need atleast 65% aggregate marks. It is 75% for general candidate.

If you are a average student and know your capabilities then you have to work hard, study hard, concentrate and be focus on your studies only and not anything else .
Just go with the concepts of subject of 11th and 12th , practice NCERT as much as you can, Try to solve every question of the book. Go for previous year paper if you want to go for coaching then choose good coaching for the preparation but do not totally depend on it. Do more self study.
You will definitely qualify for 1 attempt in JEE Main.Also if you are of general category then actually you have to study hard.

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.

Hello Debargha Samanta,
Keep these points in mind before starting preparation for IIT:
Time management
Follow a schedule / prepare a plan.
Know the syllabus and the exam pattern well, weightage.
Coaching classes online or offline? Self-study.
Study concepts, solve problems and look at solutions.
Solve previous year's papers.
Take timed practice test series.
Group study, hangout more with toppers
Health is wealth.
Manage Distractions through self-control app.
Retrospect your day.