Hey Adarsh,
Yes you can take B.Tech course after completion of diploma in engineering. B.Tech course will allow you to directly take admissions to the second year of engineering. 

For taking admissions in B.Tech, you must have to complete 3 years in diploma after 10th in any branch of engineering.

Some colleges take admission through lateral entry exams like Joint Entrance Examination of Lateral Entry ( JELET), Diploma to Degree Entrance Competitive exam, Etc. So you need to appear and crack these exas. Some colleges conduct their own entrance exam for getting entry.

Admission procedure varies from college to college. So you will have to contact colleges individually.

Hey,
Yes ofcourse you can this is because diploma after 10th is considered to be equivalent to 10+2. But yes make sure the stream is same in diploma as well as in B.tech. You cant go like ECE Diploma and then B.Tech in CSE.
Hope this helps.
Thankyou for contacting Coareers 360

Yes definitely you will get as a lateral entry in Second year directly.