Power of natural guardians before HMGA 1956

Plaintiff’s argument: X a widow of Z is the natural guardian of A and B as both are minors. X sold inherited properties of Z to Y in 1929 & 1931. Plaintiff says that the property was sold for the benefit of the minor as well as personal covenant. Defendant’s argument: X never sold any property to Y because X has no right to do so without court permission for her individual interest. Section 8(2) of Hindu minority and guardianship act 1956: The natural guardian shall not, without the previous permission of the court,- (a) mortgage or charge, or transfer by sale, gift, exchange or otherwise, any part of the immovable property of the minor, or (b) lease any part of such property for a term exceeding five years or for a term extending more than one year beyond the date on which the minor will attain majority. Plaintiff argument: The transaction took place in 1929 & 1931 when Hindu minority and guardianship act 1956 was not enforced. So X has no restriction to sell the property and also does not requires and court permission. So here we are the defendants, how will we prove that in 1929 and 1931 X has no power to sell any kind of property related to the minor without court’s permission. We have to prove that X never sold any property to anyone when she was the natural guardian of her minor Childs after her husband’s death.