GST on society maintenance by Commercial Complex

Hi,

I am aware that Resident and Housing societies have exemption from GST if the monthly maintenance is below Rs 7,500 or Annual turnover is below Rs 20,00,000.

However I would be glad if you could answer following questions regarding commercial complex:

1. Is GST applicable on maintenance charges even if the annual 20 lakhs limit is not crossed?
2. What is included in calculation of turnover for checking the annual 20 lakhs limit? Is it whole amount collected by society from it's members (including common electricity/property tax/water charges)? or just the amount towards society maintenance?  
3. If the commercial society has taken voluntary registration, then would it have to charge GST even if the limit of Rs 20 lakhs is not crossed?
4. Can the society stop charging GST in future if it's annual turnover subsequently falls below 20 lakhs?
5. On what elements in the society maintenance bill can the society charge GST?

Thank you in advance.