Hello Buddy! Hope you're doing good.

As you are eligible to get a seat in IIIT with CS then it's quite good to take admission out there. But you want to get a seat in any IIT then with partial drop, you will not achieve that goal. And if you are not sure then take admission and study hard and again give JEE next year, if you get a seat next year in IIT then it's good and if not then not to worry. Being in a CS branch in any recorgnised institute is good for fututre too. For knowing your possibilities of getting a seat you can use the college predictor tool given below :-

https://engineering.careers360.com/jee-main-college-predictor?utm_source=qna&utm_medium=jee_cp

Hope this will help you.

ALL THE BEST! WORK HARD !!