Aviation

There are multiple aviation academies you could join if you fulfill all the criteria laid out by them.

There are multiple choices for you, ranging from short term courses to degree courses. Depending on what you want to do in the aviation industry this would change.

Credit Control Manager, Airport Manager, Test Manager, programme Manager, Assistant Airport Manager, Airport Operations Manager, etc. In areas such as Aviation Industry, Airline/Port, Airline Insurance, Airline Contracting, Recovery and Credit, Sales Operation, etc.
The average full time fee charged for the course in India ranges between INR 18,000 to 2.6 Lacs for each year, and the average annual salary offered to such professionals varies from INR 2 to 6 Lacs per annum, increasing with experience and expertise.

You haven't mentioned the name of any particular institute or establishment. However, there are various establishment that offers short-term courses about aviation specific jobs.

You need to know which colleges or academy is conducting the exam, and then you can go for it.

No, you need to have a min 60% and that too with PCM not PCB.

It is better to complete your class 12th first, ,as the eligibility is 18+, so you can easily go for that even after completing your class 12th.