Hey Manav,

There are many ways to get admission in B,Tech after diploma. One way is to get direct admission. Some college takes admission directly by looking at candidates diploma marks. And the candidates need to appear for state exams to get a lateral entry. Lateral entry scheme is intended to admit meritorious Diploma holders to the second year of the B.Tech courses to acquire a degree in engineering. The top-notch colleges of the country have the provision to Lateral entry for a diploma. They have a fixed number of seats allotted for students. Students entering directly through lateral entry, complete their engineering in 3 years or 6 semesters. The exam procedure, the course, and the degree everything remains the same for the applying candidates. 

The Eligibility criteria are The general eligibility for B.Tech Lateral Entry is 60% in Diploma (Engg.) (any stream) (3yrs. after 10th or 2 yrs after 10+2) and it may vary from college to college.

Hope that helps

all the best