1. The property acquired by your grandfather by a partition among his siblings shall be his own and absolute property.
He had already transferred his 2/3rd share in the property to your mother without taking the consent of his other children, which clearly establishment that he is the absolute owner of the entire proeprty.
Therefore your mother cannot claim any share in the remaining property as a right at least not during the lifetime of your fatherland.
2. This may lead to the anticipated controversy and your mother may have to struggle to protect her interests in the property already transferred to her name.
3. It is not a conditional gift deed, it is a recital to make clear that she do not have any rights over the remaining property.