Hi Anurag, I think yes, you can get seat in IISER but it is quite difficult. The competition has been going up really high over the last few years, so inorder to get into the most deemed IISER's usually high score is required.

However, if you have availed the float options and if you have luck on your side, then if not in the first round, in second or third round you may be shot at the IISER.

Best of luck!