You cant "make" a function a friend to a class without the class "giving away" its friendship to that function. means?

Answer 1

It means it (being a 'friend' and having access to the private members of the class) must be explicitly granted by the class.

This is done by the class duplicating the function declaration inside the class, and adding the friend attribute to this declaration.

Basically, the class controls who its friends are.

Answer 2

according to me it means that the first class will provide its members to friend class under any circumstances