I am going to purchase a flat of land owner share in a newly constructed apartment (95% completed possession in june 2015 ) in Mumbai. Please clear my doubts.

1.whether I can get exemption of VAT & SERVICE TAX ?(Landowner already paid service tax and vat and registry is also done i am second owner of the flat)
2.Its safe to buy flats from landowners?
3.what documents i need to cross-check?
4.Tri-Party agreement is required(Landowner done his registry with builder i am second owner of flat).
5. Anything else required please guide me coz this is my first flat and i am not very much aware about property documents.

Thanks in advance.