IIT

Yes, you will definitely get admission in an IIT.
You scored very good marks in JEE Advanced.
No need to worry about it.
https://www.resonance.ac.in/reso/news/jee-advanced-branch-allotment.aspx
Check this branch and IIT college predictor.

There is a link below that will help you find a college that you might get into with your score/rank:
https://www.resonance.ac.in/reso/news/jee-advanced-branch-allotment.aspx

This year JEE main cutoff for sc category was 32 while cutoff for advanced is
GENERAL CATEGORY-128
OBC -115
SC/ST-64.
You should have good marks to get admission in IITs.
I hope it helps.

Varanasi has many good coaching centers for entrance examination. I will suggest you to join JRS tutorials. You have be determined and focused to clear JEE with a good rank. All the best.

Chances are there but can't say surely. You may wait till spot round counselling. You can also try CSE related Branches like mathematics and computing IT etc.

Yes, you can. But, it depends on the other students of your category. I will suggest you to wait for the spot round or last round. You may get lower branches.

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