IIT

for chemistry you should go for o.p tandon and for physics you should go for resnik and halliday or d.c pandey

Yes you can fill the form after you clear the compartment exams. However you must have a minimum of 75% which is the JEE Mains cut offs. Hope it helps.

Hi Harshit,
You may refer to what Sunil Soni advised you here-
https://ask.shiksha.com/am-i-taking-a-risk-of-dropping-1-year-for-cracking-iit-after-i-passed-12th-cbse-board-please-guide-me-in-this-qna-3682543
Good Luck

Depends on ur category

Hi
It would be little difficult to manage both as JEE preparation require regular studies and hard work. If you are very sure of doing something from IITs only, then u may take a gap year and prepare rigorously for it. Otherwise continue with ur b.tech. Alternatively, if you can manage both, u may try again.

if you are thing about cracking iit remember it's very very hard and it's not a child play . to prepare for iit you must first forget about your board exams as they will be an obstacle for your dreams + board will be thrown out of jee mains next year so it won't matter anyway
you need to study at least 10 hours a day and clear each and every dought you have . forget about your friends relative and family it's study should be your religion

Hi
For any engg related diploma, you need to hv sciences as your core subject. Check here for more details.
http://jobsandeducationalerts.com/delhi-iti-admission-2016/