What study level should I choose in U.S.A. after Diploma in Mech. Engg. from India?

Hello!

       I have completed 10th. std. + 3 years Diploma in Mech. Engg. from India.

For further study, which level of degree should I select ex. Undergraduate/ High School Diploma/ Associate Degree?

I am interested in aviation industry, which subject should I select : pilot, cabin crew and how can I get admission in it?

What procedure shoule be done for admission as I hold F4 visa category?

Thank You!

Yours Faithfully,

Looking at your profile, you should apply for Undergraduate. Maybe you can waive some course credits in Undergrad with your extra year of coursework, but it all depends.
Your choice of course, should be based on what you like and what is your passion. First decide on what you want to be.
Well, you should check with DSO at any American school on the visa specific requirements. I am not very familiar with F4 visa.