B.Tech

For which college you are asking about?

Kindly use the JEE Mains college predictor for shortlisted colleges based on your percentile.
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor
Check out this link for more details of the course : https://www.shiksha.com/b-tech/course/b-tech-in-mechanical-engineering-walchand-college-of-engineering-sangli-190751

As per the information available on GITAM college website the admissions in B.Tech programs are based on the performance of GAT (UGTP) an entrance test. Further, 60% marks are required in PCM and aggregate at class 12th level. Hence, GITAM does not offers admission to engineering Diploma holders.

In GGSIPU admission is through counseling based on the rank obtained in Guru Gobind Singh Indraprastha University Common Entrance Test (GGSIPU CET).
You can check this link for more details : https://www.shiksha.com/b-tech/course/b-tech-lateral-entry-guru-gobind-singh-indraprastha-university-dwarka-delhi-273913

Hello Mohan,
Yes, there are part time courses available.
You will have to come to the college during the weekends and the full time staff will be taking classes for you. You may consult to the college authorities for more details.
All the best.

Yes, there are part time courses available in SRM University. You will have to come to the college during the weekends and the full time staff will be taking classes for you. You may contact to the respective authorities for more details.
All the best.

Yes, there exists an entrance exam for B.Tech part time courses.
Hope, that answers you question.
All the Best.

Yes, you can. You can enroll in any university through B.Tech lateral entry exam. Different universities have different criteria, so you need to check their criteria like your score in Diploma and several or mostly universities conduct B.Tech lateral entry exam for this purpose. Stay updated with the procedure and prepare well with your basics learnt during Diploma.

No, without mathematics, how will you appear for the engineering entrance exams. In engineering entrance exams, you are tested for three subjects mainly physics, chemistry and mathematics. So, you need to have mathematics, as your one of subjects either in main or optional form.