MBA/PGDM

Salaries may depend on which colleges you choose and how much efforts you put in. In top MBA schools, average salaries are Rs.14 lakhs but it requires CAT, GMAT percent of 99+.

It is not necessary, but in case they have linguistic minority quota, you may need to produce it.

It is the general misconception that MBA has no job opportunities. However, if you are doing MBA then it should be at the top B-schools, which offer good placement and packages.
Before doing MBA in London, please refer to the previous placements that B-School has offered to the graduates.

Yes, you can get government colleges. Kindly tell us which entrance exam you have given so that we can guide you properly.

680 is a very good score, but you have less chances as they call at 700+ scores for GMAT. Fees for two years is around 17 lakhs.

PGDM from IMT is highly recommended and is the best amongst above colleges you mentioned for brand value, placements and internship opportunity, international jobs, faculty and grooming. PGDM and MBA have equal weightage and both can be done.

Tourism management is niche and new course and has good job profiles and variety of sectors can offer you jobs.
https://www.shiksha.com/tourism-management-article-4629-1

Gap of a year or two will not have much impact till the time it is explainable. If the justification is valid, then you do not need to worry about the same. Just focus on getting a good score in whatever exam you might be approaching.

Depends on your area of specialization and the college you take admission in.

Not good. I strictly recommend you to do MBA from reputable B-school ranked under top 50. Else it holds no value and would just incur you huge cost.