I've completed my Diploma from Haryana college. Can I get lateral admission in B.Tech in Delhi?

After pursuing your Diploma degree from any place, you can seek admission in any of the college as a lateral entry around any place. There is no such restrictions to do Diploma and B.Tech from same college and same place.

LEET is the name of the category of Lateral Entry you are eligible. If you have any willingness to come out of Delhi for an affordable engineering, TERII-Kurukshetra can be a good option.