Diploma

You have asked a very critical enquiry. I say so because you have done 12th and also Diploma. What it means is that you have passed Diploma in 2017 and if you had done this after your 12th then you must have passed 12th at least three years before. Normally for getting admission in NIT or IIT etc. , 3 years window is provided but IIT's also accept Diploma as equivalent to 12th. But I am afraid, my own reading tells me that you are not eligible. But you can still seek clarification on an individual basis from NTA or the agency conducting the exam.

Its nice to know your intention of joining GMR Aviation Academy I am attaching a link that will give you all the required information about this Academy and various courses which they conduct but it seems that all their courses are at the level of post graduation meaning for all the courses eligibility is graduation in any subject. https://gmraviationacademy.org/.

Hi Alina,
You did not mention your subject, stream etc. And the question is very vague. Scope depends on the subject you choose and also your whole profile.

PFB the Diploma course details:
https://www.shiksha.com/medicine-health-sciences/medicine/colleges/diploma-courses-india?ts=84385973&rf=filters&cl[]=15&cr[]=10 (Copy paste the entire link on the browser).

Hi!
You can apply online on the official website of the institiute or you can visit the institute and fill the form offline.

Hello, For any postgraduation you should be a graduate. All the best
If you find this helpful do give an upvote.

Hi Rohan,
No, you cannot eligible for JEE examination.
Candidates still can appear in JEE Main exam three times in three consecutive years. For more query we can visit on this
https://jeemain.nic.in/webinfo/Public/Home.aspx
Best of luck.

Yes, you can. But, please check the eligibility of age required to get admission in the college of your choice. Thanks and best of luck.

Hello,
You can pursue 3 months PG certificate in desired field from FTII. In my knowledge, there is no 3 and 6 months Diploma course available for the same.