Is zakat obligatory on the money of a minor son, frozen in the حسبى [Hasby] Council, knowing that his guardian does not benefit from it and leaves it until he grows up?

We have no knowledge of the Guardianship Council (al-Majlis al-Hasabi). However, the guardian of the child must pay zakat on the child's money if it reaches the nisab (minimum threshold) and a hawl (one lunar year) has passed on it.