B.A

Yes, you can do MBA. Anyone can do it, if one has completed graduation with at least 50%.

Hindi honors is a best option. A post graduate degree can lead you to UGC NET. You can pursue journalism and your skills of Hindi will open new horizons for you as there are huge needs of Hindi writers and speakers. Content writing is a good option.

You may apply for MA or MBA program.

Hi Devendra,
Diploma in mechanical is a good choice to make your career in mechanical either design or core mechanics. I don't know what makes you want to take tourism. Both the courses are different in nature and career opportunities.If you want to start your career in tourism, then go for it, but think why you opted for tourism course? Think about the options you have at present in mechanical. Compare both the fields and scope they have. Remember degree is not enough to start your career.
Can I know the reason behind your decision?

BA economics (Hons.) is mainly theoretical and B.Sc in economics have maths with economics. Both are good options. Your choice must depend on your interest.

If you have will, dedication and readiness to put extra efforts to prepare for Civil Services along with your graduation studies, then you must go ahead.
All the best.

Yes, but you've to search for the institutes which offers the concern subjects.