JEE

You should appear for JEE mains first, if you clear that exam then you should appear JEE advance.

Yes, every candidate who appeared for JEE main and has been allotted AIR is eligible for JOSAA counselling, but the seats are allotted on the basis of merit. You can fill in your choices for the spot round.
Best of luck.

You can visit the below mentioned link:
www.freeiitcoaching.com

No, it's only for JEE advance.

Every student have its own learning and grasping capacity, time table is a person specific thing. You are the best judge of your strengths and weaknesses and the amount of time you need to spend daily. Keeping that into consideration design the time table.

Akash Institute is the best coaching institute in Assam.
All the best.

You need to choose a good coaching center and have confidence in yourself. In the end, your efforts will matter. You can solve previous year papers and model papers.
All the best.

JEE Mains and Advanced exams will make you eligible to seek admission in IIT, IIST and PEC university. These are India's best institutes for aeronautical engineering. You can also appear for Manipal and Amity university exams to join aeronautical engineering degree courses.

This actually depends on whether you are comfortable with coaching or not. Because, there are many students taking coaching and getting good marks but there are also many students who opt self-study rather than joining the coaching. So, it depends upon your level of preparation and confidence.