B.Arch

First of all, I should appreciate your confidence of getting 250+ in JEE Mains. It is not an easy stuff to score that much. Coming to the ranks, it depends on the range of difficulty of the paper. If the paper is difficult then there is a good chance of getting good rank if you get 250+ and if the difficulty level of the paper is more, more number of students would score more than 250 so the chances of getting good rank decreases.

Please refer to the link below to know about the eligibility and other details:
https://www.shiksha.com/architecture-planning/course/b-arch-college-of-engineering-trivandrum-thiruvananthapuram-181429

Dear,
You can do B.Arch through lateral entry after completion of Diploma in civil from AICTE approved institute. But before admission you might have to clear NATA with valid score. Better you search the institute's site where you intend to get admitted. Best wishes.

Hi Elisha, Please visit our website www.ceptadmissions.in.

Hi Aishwarya, For B.Arch. At CEPT University, it is mandatory to qualify NATA.

Dear Divya,
There are total 80 seats wherein 40 seats are filled by ACPC (Gujarat Students) and 40 are All India seats. Gujarat students can apply in All India seats as well. But the quota for Gujarat State Board students will be in ACPC seats.

Yashwantrao Chavan Maharashtra Open University offers B.Arch. The eligibility criterion is 10+2 with a minimum of 50 percent marks and mathematics as a subject and a minimum of 40 percent score in NATA. The institute offers Diploma in Architectural Assistantship and Building Engineering, and M.Arch also.

Dear Dhruvi, There are various scholarships offered in CEPT University. Please visit the link
http://cept.ac.in/student-services/student-financial-aid

You should go after the result of Nata 2018, and they will held a counselling by Sir J.J College of Architecture.