Property documents

Here you have no problem, that "A" is acquired the property under a Registered Sale Deed in the year 1980 and where as your vendor "F" is also acquired the said property since 2006 under a registered Sale Deed. But you have to take some more docucments (1) in case of lands: Pattedar Pass Book, Title Deed, Mutation Proceedings and pahanies for the last 30 years. And you should know, whether the land is a Government land or patta land. (2) In case of house property: take Electricity bill, Tax receipts from 1980 if have, Water Bills etc., to show the title. EC for the last 1980 required. 

That property is having 'A' khata

The total size of the property is 30x30=900 Sqft .It has a sheet house . We are buying 15x30 = 450 Sqft . It is a 'A' khatha property.The property tax is paid from the year 2000 to till date. I have asked the owner to provide the EC from 1948. what is mutation document ? What is title deed ? 

can a person give power of attorney to his son for attending court matters that may arise in future related to his share in ancestral property and will it cease after the death of the principal 

Please obtain Encumbrance certificate from the year 1975 onwards.  The power of attorney holder cannot execute another POA deed to a third party on the basis of his power deed and so on.  This transfer of power from one agent to another agent is legally invalid and any transfer of property on that basis is also invalid.  Lastly when E the power agent of D sold the property to F, the E has got no locus standi or legal position to sell the property to F.  When there is a dispute about this by B or his legal heirs, the whole sale transaction will be held as invalid and not binding on the B or his legal heirs.  Here though B has not revoked his powers executed in favor of C but on C transferring his power over the property to D, which is invalid by law, automatically cancels the power vested on him by his principal.  However such type of transactions are abundantly prevalent in many parts of the country and goes on peacefully until there arises a dispute.  Here Buyer beware will be best concept to be applied.