JEE Main

Yes, still, you have chances of you give other colleges though private ones entrances. Also, state colleges still conduct their own entrance exam. If you miss JEE you won't get admission in NIT or IIIT or IIT. But you still have chances to get other private good colleges and also state government colleges. Don't lose hope.
All the best.

Try Shiksha College predictor which gives an approximate idea of rank and colleges. You can specify the category you belong to in the predictor to know about your rank or colleges you want to shortlist.
All the best.

No, JEE Mains is all about how you have understood the topic and how you solve numericals within a short span of time. JEE is not an interview it's just an exam of your 11th and 12th subjects. Be thorough with all the topics and you will be good to go. Practice numerical as much as you can. Coming to your question the answer is no.
All the best.

If you are confident enough that you can study for one year without any diversion. Then yes you can. I am a dropper and I was self motivated to crack JEE with a very good score. And yes I did it. Everyone is capable of doing it, just don't lose hope and work hard for a year. The amount of effort should be much more than you put in 12th.
All the best.

That totally depends on the pattern and difficulty of the paper and also the number of students applying for JEE. Percentile is calculated wrt to the number of students getting marks below the respective person whom percentile is being calculated. If the students will vary they percentile may also vary. I hope you understood.

I don't know about Satyabhama if giving scholarship on the basis of JEE. They provide admission by giving their entrance exam that is SAEEE. The application process is still going on. If you want admission in that college you can fill the form and score very good rank. Where you will have a fair chances of getting scholarship. Also, the top three in semesters is awarded a scholarship which is named as Remibai Jeppiar Scholarship

Yes, it is possible but you won't get very good colleges, you can also give private colleges entrances. Some colleges also give direct admission based on 12th score as well. Even some colleges are there where you can apply and they will definitely give admission. But, JEE is the prestigious exam to enter into the reputed colleges.
All the best.

JoSAA is only for government colleges and not private colleges. You have to apply for private engineering colleges separately. Many of the private colleges accept admission on the basis of JEE Mains but you have to apply separately.