hello aspirant,

The Cutoff for JEE mains is very different for different category Students. So, since you have mentioned that you belong to ST PWD category, so in order to clear JEE mains you just have to score 12-17 marks in JEE mains out of 300. That means you just have to give correct and accurate answers for 3-5 questions in JEE mains and then you can qualify jee mains and can be eligible to appear in JEE advance.

now in JEE advance 5% of the seats are reserved fro Pwd Candidates. So If you crack JEE advance then you can easily take admission in IIT (according to the rank) . So according to the previous year Cutoff, you need to score at least 30-35 marks in JEE advance to clear IIT.

Further, to know more about the reservation policy for Various categories in JEE examination, follow the below mentioned link to know more : https://engineering.careers360.com/articles/jee-main-reservation-criteria

I hope that this will help.