JEE Advanced Eligibility

Yes, you are qualified, as the cutoff for general category is 81 this year.

Your going to JEE Advanced which depends on your reservation quota. The cut-off marks for general is 81 marks, 49 for OBC, 32 for SC and 27 for ST. Your 12th exam marks plays no part in going to give JEE Advanced. If you're unreserved, you have to give the exam again next year. Other than that, you will qualify for this year's JEE Advanced.
Best of luck for your future.

You have scored above the cut-off. So, you can write JEE Advanced.
You cannot get any IIT without JEE Advanced.
You may get NITs but not the best ones as the cut-off is 49.
The application for JEE Advanced open tomorrow. So, do it well.
All the best.

First of all, I tell you nothing is impossible, but as you attempted two times then it's little risky that next year you may crack the exam, as from next year, new pattern question may be asked, as only one paper is going to be held for engineering also, just like NEET in medical, so it is risky to do.
You can crack it, if you have really confidence that I missed the exam with little marks like that.
But, I suggest you not to waste one more year, as in future it may be questioned that where you spent these two year.
I strongly recommended you to join any college, because it is a matter of one year.

JEE rank and cutoff marks change every year. According to the last year's cut off if you score 85-95 marks in JEE Mains exam then your rank may be nearly 100000 or below or above and your eligibility to appear for JEE advance is according to this year's cutoff.

Yes, you are eligible for JEE mains, but not for JEE advance.

If your aggregate in PCM is above 60% (general), you are eligible. If you belong to OBC category, you need 50% aggregate in PCM and for SC/ST, more 4-5% relaxation.

Yes, you are eligible to appear for JEE Mains 2017.