The vacant seats reserved for SC, ST and PwD candidates will be allotted to the candidates of respective categories for admission to a preparatory course of 1 year duration on the basis of relaxed admission criteria. Admission is given to the candidates in the preparatory course provided

(i) the seats reserved for the respective category are vacant

(ii) candidates satisfy minimum norms and

(iii) candidates have not accepted a seat in the preparatory course earlier.

All the IITs run  preparatory courses of one-year duration for SC, ST and PwD candidates intended to prepare them to pursue the academic program. At the end of this course, candidates are declared as ‘pass’ or ‘fail’. On successful completion of the course, the candidates will be offered direct admission to the already allotted undergraduate course. Candidates admitted to the preparatory course are also eligible to appear in JEE (Advanced) subject to fulfilling other eligibility criteria.

You can sit in JEE Main and JEE Advance to get into NITs and IITs respectively. If You manage to qualify the exam by achieving the cut off, You can apply for JOSAA Counselling. It should be noted the cut off for EWS/SC/ST/FEMALES/OBC category is lower than the general category
However It is usually advised to fill the choices as per the preference of colleges and departments, for example CSE in NIT Trichy is your priority followed by CSE in NIT Warangal, you can fill CSE at NIT Trichy at serial number 1 and CSE at NIT Warangal at serial number 2 and so on and so forth. However to get any NIT, you must have qualified JEE Mains and to get any IIT, you must have qualifies JEE Advanced

But the previous cut offs of colleges should be taken in consideration, it is better to research over the cut off of colleges then make a preference list of colleges and fill accordingly

For the college preferences and the courses provided by these colleges and to know which colleges participate in the JOSAA counselling, please go to the below mentioned link: https://engineering.careers360.com/articles/josaa-participating-institutes/amp

For college prediction as per your marks and rank, please go through the below mentioned link:

Rest for information on any particular college, you can dig their official site for better information