2.UK marriage certificate is valid while applying for UK Visa in India. Because you are anyway applying to the British High Commission and not the Indian Govt.
3. Please use the following links to apply.
http://www.ukba.homeoffice.gov.uk/sitec ... ation1.pdf
http://www.ukba.homeoffice.gov.uk/sitec ... olicy1.pdf
4. You can use either of them whether you are applying in UK or in India. Just need to satisfy all the criteria.
5. Nope. For dependent applications cooling off period is not mandatory.
Your application is just a cake walk. Just complete the TIER 2 (dependent) application, attach the necessary documents,
Relax and enjoy your married life.