B.Tech Eligibility

At the time of admission, you need to pay the hostel fees and mess fee which is around 50k, that's it.

Yes, you can join B.Tech after completing Diploma in Mechanical Engineering. As you have completed Diploma in Mechanical Engineering, so you can join B.Tech in Mechanical Engineering, Aeronautical Engineering and Automobile Engineering only. You can get admission in Engineering colleges through lateral entry scheme.
According to the lateral entry scheme, you can get admission in an engineering college for B.Tech course directly in the second year.

You should have 75% in class 12th. You have to pass the written exam and an interview.

No, you can't as science subjects are must to get admission in B.Tech.

Hello Velpula,
You have scored very well in your boards and there are some colleges which take admission via boards marks like SASTRA University, Thapar University, etc. but I will suggest you to wait for 1 year and prepare well for IIT-JEE, you will definitely get a good college.

Yes, you can get admission if second counselling round will take place.

Yes, NIOS board marks are accepted all over India. Just contact the college for admission as the dates are going to be over soon.

It's a decent college but to know the exact scenario for faculty and placements get in touch with the current students through social media or in person.
Check the link below for more details:
https://www.shiksha.com/college/techno-india-salt-lake-salt-lake-city-kolkata-48911/reviews

Well, distance courses don't have stringent age criteria but you are 42 now so it might create some problem. For details, you must contact the college from where you are planning to pursue the course.

Dual degree B.Tech-M.Tech in biotechnology are eligible to seek admission in M.Phil and PhDs.