Diploma

Yes, you can do Diploma in aviation from JIMS and you can do it from UPES also, these both are the best universities for aviation courses. You can apply for this course from distance learning UPES.

For doing Diploma in fashion designing you must complete your 10+2 as it is the eligibility for doing this course.

Eligibility Criteria for admission:
Candidate must have passed 10+2 from a recognised board.
https://www.shiksha.com/design/interior-design/course/diploma-in-interior-designing-ymca-new-delhi-connaught-place-255402

Eligibility: Minimum 50% required in class 10th.
Age: Maximum 22 years
Other eligibility criteria:
Age limit should not exceed 25 years for SC/ST candidates.
This course is available only for male candidates.
Admission Process:
Register and Apply-Interested candidates can apply online/ offline with the re

I am attaching a link below, go through that link to get all the details:
https://www.shiksha.com/b-tech/course/b-tech-in-marine-engineering-lateral-entry-indian-maritime-university-Chennai-Mumbai-campus-merit-sewree-296923

Sorry, but many people are studying to become an engineer or doctor but what is a guarantee of job after 4 or 5 years, most important thing in airlines and aviation is that it is a growing industry. Nobody can stop you, if once you are skillful in your field. Just be confident