Diploma

Hello Sujit,
Yes, you can seek admission in Aerospace engineering after Diploma in mechanical. Diploma is considered as equivalent to class 12th for admission to IIT and many colleges.

Dear Akshay Bhoite,
To get admission in engineering after doing diploma engineering you will have to appear in LEET entrance exam conducted by each state university every year.

Please check the college details as per your marks, rank, branch and category in the link provided
below:
https://www.shiksha.com/b-tech/resources/mhcet-college-predictor
All the best.

To get a job as an Air Hostess, your personality is more important than the education.
If you really want, then go for it.
Please follow the link:
http://surejob.in/how-to-become-an-airhostess.html
All the best.

I will suggest you take lateral entry admission in the 2nd year of engineering (B.Tech).You have to quality lateral entry examination conducted by various universities and colleges.

You might have done a Diploma through Polytechnic which is equivalent to XII and will lead to a degree eligibility, because, for mass communication or media related courses, the XII background does not matter. If you have completed class 12th then it becomes easier for you to pursue UG.

You can pursue a Diploma course in photography for sure. Symbiosis has a dedicated school for this. Apart from them, other mass media institutions have photography as an important part of their electronic media courses. Video production also covers this.
There are online courses for photography as well.

The PG Diploma can be done any anyone who has a Bachelor Degree. The qualification you have already earned are supporting your claim to be a good learner, but are in no way an issue in doing the PG Diploma in Journalism and Mass Communication which is a one year course.

You can take admission in that colleges:
Indian institute of technology, Hyderabad
IIIT International Institute of Information Technology, Hyderabad
NIT National Institute of Technology, Warangalwarangal
JNTUH, Hyderabad
OU College Of Engineering, Hyderabad
CBIT, Chaitanya Bharathi Institute of Technology, Gandipet, Hyderabad
BITS, Pilani, Hyderabad
MVSR, Maturi Venkata Subba Rao Engineering College, Hyderabad
VJEC, VNR Vignana Jyothi Institute of Engineering and Technology,
JNKRJ, Ntuh College 0f Engineering, Nachupally