The basic difference between a B. Tech and diploma is that a B. Tech is a degree course while a diploma is a course in engineering. 

One can opt for diploma just after 10th or it can be after 12th. But one can opt for B. Tech only after 12th with physics, chemistry, mathematics. 

Diploma is of minimum 3 years but you can take a lateral entry in diploma if you have done ITI for which the duration of course will then be 2 years. 

Btech course is for 4 years, admissions are based on a lot of entrance examinations like JEE, VITEEE, BITSAT. 

Hope this helps to clear out your doubt. We are here for any more queries. 

Hello gaurav

B.Tech is a degree course while polytechnic is a diploma course in engineering. 

If you do polytechnic after 12th you need to do b.tech as graduation. But if you directly do b.tech then no need of polytechnic because b.tech is a higher degree than polytechnic.

Polytechnic can be done after 10th standard also but you cannot do b.tech after 10th.