Documents Reqd. MSME Registration?

Hello Everyone, 

We are into Consulting business and provide our services to Corporate clients. We would like to register for MSME. Need your help in getting answers to the few questions:

1. What are the documents reqd. for registration in case it is a Proprietorship Service firm?
2. Can we register for MSME anytime of the year?
3. Do you think it is beneficial for a startup to register for MSME?
4. Do we need to file any additional returns if we enrol?

Thanks in advance for all the help in advance!

Regards, 
Mayur