can we make an object of parent class in a variable of child class through casting?

yeah, as you illustrate child has all properties even public and internal methods of parent, my question starts from here, if child is capable of taking all properties except private members and fields, than why the functionality or power of child is limited, it has to become more powerful then parent, but the reality is that the parent is more powerful it can contain the object of child but child can't do this, please reply me if you have any idea........