Religious Duty of a Backward Person    
The criterion for religious duties becoming obligatory upon any person is their shar‘ī puberty, in addition to being recognized by common people as a sane person. The varying levels of intelligence and comprehension are not a criterion and have no bearing whatsoever on this matter.

The Signs of Puberty
The signs of puberty are as follows:
1- Growth of coarse hair on pubic area
2- Discharge of semen
3- Completion of 15 lunar years (which approximates 14 solar years, 6 months and 17 days) for boy, and 9 lunar years (which approximates 8 solar years, 8 months and 22 days) for a girl.

Custody /Guardianship of a Minor Orphan
The paternal grandfather has the right of shar‘ī guardianship of the minor orphans and their properties. The mother has the right of their custody. 
To Use a Child's Property
It is permissible for the guardian of a child to do, with the clothes or things like toys gifted to a child, what he deems fit, taking into consideration the child’s interest and welfare.

To Use a Child's Property
It is permissible for the guardian of a child to do, with the clothes or things like toys gifted to a child, what he deems fit, taking into consideration the child’s interest and welfare.