hi,
see in case you have finally submitted the form with payment you may not correct it. In official information brochure there is no mention of correction facility. however for any kind of admission related issue you may send your query to below mentioned email address and wait for the response.
admissions@iitd.ac.in (IIT Delhi)
To know about complete list of probable college name, based on your score, category please use Careers360 college predictor tool,
https://engineering.careers360.com/gate-college-predictor?icn=QnA&ici=qna_answer
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