(i) Ram,s father purchase this property in the name of three son. Hence this is gift to ram from his father. Therefore shall it be call ancestral property.
Though Ram's father funded for the purchase of this property, since he bought the same on his sons names, this property shall belong to his three sons only. This cannot be considered as ancestral property.
(ii) if this not an ancestral property then will there be any share of mother of the death of her son
Yes the mother being a legal heir to the son, she is entitled to a share out of her son's properties besides other legal heirs.
(iii) Grandmother has already made a registered will in fabour of Ram's son on December,2016 but still Ram's mother can transfer her share on deceased son(Ram)'s property to another son( sankar) though fresh registration.
The Will shall come into force only after the lifetime of the grandmother whereas she can transfer the property by a registered deed to any other person during her lifetime, thereby the will stands automatically canceled becasue there is nothing to enforce in the will.