Hi Adhi,

Admissions to all IIITs is through JEE Main. However, IIIT Hyd, Delhi and Bhubaneshwar conduct their own admission process on the basis of the JEE Main scores. Except for these three, admissions is through JoSAA counselling and eligibility criteria is obtaining 75% in Class XII (ST/ST 65%) or being in the top 20 percentile of the class 12 board. All seats in the IIITs through JoSSA are all india. IIIT Bhubaneshwar has 50% of the seats reserved for Odisha candidates and the eligibility is same as JEE Main plus an aggregate of 60% in class X, 60% in Class XII in science and a minimum of 45% in each Physics, Maths and Chemistry.
As for the minimum ranks, you can check this article - https://engineering.careers360.com/articles/jee-main-cutoff-for-top-iiits

All the best!

Hope it helps! Comment Down if you have any other queries... Goodluck!