CBSE 10th

Hi,
NIT score is above 80, the various college has their own entrance test, and you can give it a try. You can also get direct admission without any entrance exam in some private universities. Candidates must have completed graduation in any stream or equivalent from recognised University in India with a minimum aggregate of 50% marks all over 45% (SE/ST).
Here is the list of Top MBA colleges
1. ISBR Business School Bangalore
2. Acharya School of Business Bangalore
3. FIIB MBA Delhi
4. Alliance University MBA
5. Christ University MBA
6. Symbiosis MBA School
7. IFIM-Business School
8. ISBM Pune
9. ITM Navi Mumbai
10. ISME Bangalore.

Hi
Yes, the cut off of CMAT is 80. Then you are eligible to get a seat in Welingkar Mumbai. You can use these links also:
https://www.shiksha.com/mba/cmat-exam-results
https://www.shiksha.com/mba/cmat-exam-cutoff

Keeping the last year of trends into consideration, the expected CAT percentile of NIT Trichy is above 80. Hence, your chances for admission are moderate here.

You can take UPSC exam, because mininum eligibility is, Bachelor's degree from a recognized university, even if the degree is through distance.

Yes, you can do any Diploma after your class 10th .

Yes, you are eligible.

Your academic record is just decent, your CAT score is very low. The chances of getting admission are very low.

As per Maharashtra State Technical Diploma Courses Educational Institutions (Admissions) Rules 2019, The other states candidates are eligible for Institution quota only. So you have to contact to Principal Government Polytechnic, Mumbai for further details.