JEE Advanced

Yes you are. You might even get your preferred course.

280 is a decent score. State your AIR or use Shiksha college predictor service.

It will depend on the cut-off marks of Advanced and only from that, you will be able to get the desired rank.

Yes you're eligible if you qualify JEE Advanced than you can give AAT exam, center would be the nearest zonal IIT.

You can see last year cutoff here:
https://www.shiksha.com/b-tech/articles/iit-qualifying-marks-for-jee-advanced-2018-released-blogId-17121

As you told that you have interest in every field I think you are an all-rounder. Jokes apart, all these courses are professional courses. You can't do this and that, and my best opinion is that choose as per your interest. And choose wisely. At this rank and mark, you can't get IIT.

IIT tag is surely worth a year but only if you are willing to sacrifice most of the things. Hard work always pays. But on the other hand, if you feel that NIT is worth it, then you should give it a try.

As you are in general category, you may not get high-level branches. But still, keep on trying till the last round.
All the best.

Hello, Shaily. First of all, good luck. I hope you will do well in near future. For physics you can consider these books:
1-Engage (most important)- Independent edition
2-TMH-As a whole worthy
3-ML Khanna-Coordinate Geometry
4-Admit M Agrawal -Differential & Integral Calculus only
I am not mentioning boo

Hello,
Hope you are doing well. Yes, definitely you can again go for JEE Mains 2019 by taking drop for ab year. I appreciate your interest for JEE Mains and goal for IIT. You should definitely go for JEE Mains I am sure you can crack JEE Advanced with this motive. All The Best for future and for JEE