Polytechnic

Shah & Anchor Kutchhi Polytechnic, Chembur is a better choice in every aspect.

Please specify, which classes are you talking about?

There can be two choices -
If you have scored a good percentage in 12th board exams then you can prepare for JEE Mains by yourself. For this, you can also refer to the study material of ALLEN, RESONANCE or VIBRANT coaching institute. In this case, you can complete your first year of polytechnic also.
The second one is, if you have not secured good percentage in 12th boards then refer to a good coaching institute and try to score good marks in JEE Mains.

Sorry, you can't do it as it requires 10+2 but you can apply for lateral entry in best college like MIT or government college without doing JEE Mains in B.Tech. it's an easier way but you can not appear for IIT.

It completely depends on your interest. If you want to gain more valuable degree, then wait 1 year, prepare yourself and get admission in a good college or you can go for polytechnic and after completion of 3 years, you can directly get into B.Tech.

Diploma is the education course of duration ranging from 1 to 3 year. Diploma can be done in any specialized subject. Colleges which provide diploma course in engineering field are called as polytechnic college.

Both of them are good, but I will suggest you to go for interior designing.
1. It is a very creative field.
2. People you'll meet will be very imaginative and creative.
3. Competition is also less.
4. You can get higher wages but not in India.