IIT

u have 3 time chance for JEE Mains and 2 times chance for advance.

Currently there is no provision of lateral entry admission in IITs and NITs for Diploma engineers.

Both the exams are for different purpose, if you want to study in India go for IIT otherwise SAT for abroad, both the options are extremely good. Final call depends on your interest and preference

85%.

Check through the college predictor below :
https://www.resonance.ac.in/reso/news/JEE-Advanced-Branch-Allotment.aspx

Abhishek, I doubt if you will get IIT with these marks, so go whatever college, whether government or private.
Otherwise, try for admission in some private university yourself. They offer you admission on JEE scores/ tests conducted by them/ your marks in 12th. Some of these also offer good scholarships based on any one of the above mentioned admission criteria.
Check the websites of some good universities or call on their toll free no.s for more details.
Good luck.

Yes you can, IIT Delhi, Kanpur and Mumbai offers post graduate course in robotics.

Yes. One can study B.Tech in Biotechnology in IIT Kanpur, IIT Roorkee, IIT Guwahati etc.

No u can't. First u have to give JEE Mains then JEE Advanced.