IIT

It is quite tough to get it as your JEE Advanced rank is too low but don't worry, just check the closing rank of different IITs by this link:
http://josaa.nic.in/Result2016/result/OpeningClosingRank.aspx

This year onward, you have to score at least 75% in class 12 marks if not then you have to be placed in top 20 percentile of your bored so if you are in top 20 percentile of your board then you are eligible for IIT exam 2018.
Regards.

Quite tough to get IITs but please check the closing rank of different IITs by josaa according to category:
http://josaa.nic.in/Result2016/result/OpeningClosingRank.aspx

Yes, why not. You can but as IITs are most reputed college in India so you have to be highly qualified to get admission here as today results of JEE Advanced exam is declared and hope you got the results and scored enough to get IITs. Please check the closing rank of IITs by JOSAA:
http://josaa.nic.in/Result2016/result/OpeningClosingRank.aspx

Hello Piyush,
Congrats for securing for a good rank in JEE Advance, if you have to choose between the above two options, definitely go for IIT Powai, for the reputation and also you can change branch after you score decent in first year.
All the Best!

You cannot sit for counselling of NITs. Else, you can get admissions on the basis of your JEE score. Find a link below that will help you to find a college suitable for your rank:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor
Hope this helps you.

If you are determined enough to crack JEE or you think that you will crack it the go for it otherwise you should settle with the available options. One year is very important in life. You will realize this later.

No, it is not important to stay in hostel but you won't get any transport facility from the college side as well. You'll have to arrange that on your own. Moreover, college hostel is most convenient as per my experience till date.

Yes, you definitely can appear for IIT JEE if you clear cut-off for the eligibility. For that you have to appear for JEE Mains.

Hello Anish,
Yes, you can change the branches from biotechnology to chemical engineering and any other choices. The only way is to have a high score in the semester exams like 9/10 or more CGPA/CPI. The one with a high score will be given the first preference. In case of a tie, JEE Advanced ranks will be used.
I think this provision is available in all IITs.
But, you cannot change from B.SC to B.Tech, as they are two different streams.