With a score of 135/300, you may expect your Rank anywhere between 30-35k. At this rank, I dont believe you may secure a seat in CSE, Mathematics or IT at any NIT or Old IIITs. However there are many new IIITs and GFTI where you may be able to secure a seat at this Rank. They are

IIITs at Nagpur, Kurnool, Bhopal, Dharwad, Vadodara, Bhagalpur and Agartala.

You may have slight chances even in Lower NITs like Srinagar, Andhra Pradesh and Uttarakhand and ones in the Northeast like Manipur and Nagaland.

However at this score, with VIT Vellore taking admissions through JEE Main score in 2021, you may easily be able to secure a seat in either of CSE or IT.

VIT Vellore is one of the leading private universities with excellent faculty, infrastructure and research facilties.

Hi.

JEE is a super competitive exam, nationwide. You will not be able to get branches with high demand such as IT or CSE with 135 marks. Tentatively, you need to get 160+ marks for better chances of these courses in NIT and IIIT.

Good Luck