When will strong features be released in ARC on iOS?

I have a quick question about ARC in iOS. (Sorry I asked so many of these questions, but I'm just confused about memory management.). It is important to note that I have never used the old storage service system ( retain, release, assign... etc), so I do not know what these terms mean.

Right now, I'm confused about what I need to do to make sure that strong properties will be released properly. For example, suppose I create a school application and my object Schoolcontains strong references to the properties of 5 different objects Child(and not in an array). Each object Childhas a strong pointer (property) for the object Book.

If I delete one of the objects Childfrom my school (say, by creating its property = nil or changing my property to point to a new object), will it be released correctly Book? What do I need to do to make sure this is so? Do I need to write self.myBook = nilin a method dealloc? What if I Childwas a view controller, do I need to write self.myBook = nilin the viewDidUnload method?

I focus only on iOS 5 (and above), so the old way of managing memory for me doesn't really matter.