IIIT

IITs and IIITs do not have the provision for lateral entry admission in 2nd year in their graduation programs.

To get admission in NIT, a candidate must appear for JEE Mains. Unless, you appear for the entrance exam you won't get admission in National Institute of Technology. The eligibility criteria for entrance exam is class 12th with PCM as the subjects.
Apart from IIT and NIT, most colleges in India offer lateral entry for Diploma students. These colleges do reserve some seats for lateral entry students.
All the best.

Hello Subhadip,
The score required to get into NIT or IIIT varies from institute to institute. If you study hard and score reasonably, then you can definitely get admission under OBC quota in one of these institutions.

IIIT, Bhubaneswar is a government college in Orissa, but for lateral entry you have to appear in LEET exam, but if seat is not available then you can't get the lateral entry admission.

Yes, you can get admission in IIIT's through JEE mains only and from next year, class 12th percentage will not be given weightage. You just need to score minimum 75% in class 12th to be eligible for JEE mains.

Indian Institute of Information Technology is a group of educational centers in India that focus on information technology and associated business requirements. There center are sponsored by the central government.

Refer the link for details:
http://www.eduarena.com/aieee-opening-closing-ranks/

There is no IIIT in Guwahati. IIT - Guwahati is available.