JEE Advanced

For admissions this year, a new caste certificate after April 2018 will be deemed valid.

Yes, there are many examples of this, the main thing is that the Mains paper is solved by smart work rather than hard work.

Last time revision for JEE Advanced should comprise more of tests. Also, try to look at important formulas and concepts. Do have a sheet with formulas. Tests will make you more comfortable with strong topics and will let you know the weaker topics. There will be some extremely difficult questions, difficult to solve so better focus on strong topics.

Yes, you should. Do your best there and then wait for what happens next and don't think about admission stuff now. Study hard for now and do that part when all your exams are done.
All the best.

Yes, you are eligible because the marks need to qualify for the advance is 100. So, you are.
Regards.

Yes, you are eligible because the marks need to qualify for the advance is 100. So, you are.
Regards.

Yes, but it will depend upon the cut-off. According to some experts, the cut off this year is expected to be 98. So, you will qualify if that meets.
Regards.

If you belong to general or OBC category, then the answer is no, but if you belong to SC/ST category, you can opt for advanced.

Typically, to qualify for JEE Advanced one's rank should be below 1, 50,000. If it is above that, it's not possible to qualify for JEE Advanced. Better take a year gap and attempt in the next year.

Just concentrate on your studies and solve the previous papers. Don't take any kind of pressure, just go with the flow and ease. Keep calm, also don't put so much pressure on your mind. Keep relaxing your brain too. Study in intervals not continuous. Just concentrate and do hard work. Do best by your side, keep tracking your time that in how much time you are able to complete the questions and try to do less mistakes, if you are facing some problem while giving the exam skip it and move to it. Don't waste time in your JEE Advanced.
Best of luck.