The house sale deed had a nala in it's east, but now it's missing

I am trying to buy a house in Bangalore. All the houses surrounding this is B Khatha, but just this house has A khatha as betterment charges are paid. I am having below issues with this. Please suggest whether this property is still okay, as well let me know whether an advocate (while verifying the documents) will be able to answer all these questions (as this is related to the physical measurements) 1) 25 years earlier, Original land survey shows 24feet*40feet but afterwards (15 years earlier) the house was registered as 24feet*30feet 2) While house sale was registered to the east side of the house, in the papers it's mentioned as a nala (drainage) available but now there is no nala available (instead there is next building built near it recently). From West the measurement of the house is precisely matching (24feet*30feet) as mentioned the house sale agreement. How to confirm whether this house has encroached or the other house? 3)This is a drainage (nala), not raja kalve or any other water bodies as per bbmp survey maps. Does this have a significant legal effect on the genuinity of the property. Please let me know for any leads. Right now not looking for any paid service. Thanks a lot in advance.