Purchasing property

We are planning to purchase a plot which has a small sheet house in it in which the owner is staying. The size of the plot is 30x30= 900 Sqft. The owner is selling half the property i.e. 15x30=450 Sqft. The property is currently having  'A' khatha and the owner has paid up to date property tax.

History of the property

1. A has done Gift Deed to B in 1948. This gift deed is getting registered in 1955.

2. B and her son C have given GPA to D ( Not sure if this is registered)

3. D has done sale deed to E in 1980 (Registered)

4. E has done GPA (Notary) to F in 1988 (Not Registered)

5. F has done GPA (Notary) to G in 1988 (Not Registered)

6. G has done Sale Deed to H in 1996 (Registered)

7. H has done Sale Deed to I in 2006 (Registered)

Now I is selling the property to us. We have asked for some additional documents from the owner like EC, Gift deed copy of A to B , GPA done from B&C to D etc.

Questions:

Question 1 : Let us know if there is any risk in purchasing the property as the 2 notaries done earlier were not registered. ?

Question 2: Are there any chances of a dispute from any of the earlier parties ? If yes which party has the right for a dispute ?

Question 3: In case of a dispute what are our chances of winning ?

Question 4: Since the first Notary was done 25 years ago does it stand any chance for a dispute now ?

Question 5 : Do we need to take any precautionary measures before buying to reduce the risk ?