Suggestions reqd in buying villa - from panchayat to bbmp

[tvkbhaskar]

Dear friends, I have come across a situation and need inputs from the forum members.

A layout was formed based on panchayat approval since the locality was then under panchayat. Plan approval for villa's were also from panchayat. Locality moved under BBMP limits subsequently. All sites / villa got A-khatha after paying betterment charges. One of the site with villa is still with layout promoter and up for sale.
query 1: Though the property is currently under BBMP, plan approval is from panchayat only.
query 2: I also understand 30x40 site can get appproval from BBMP for ground + 2 floors. There is a room constructed in 3rd floor (without door) with water tank above it.
is there a risk in buying this? what are those. pls suggest, thanks.