An explanation of Nawawi's 40 Hadeeths by Shyakh Al-Uthaymeen is available in English. It is helpful in answering the questions. If you are not memorising the hadeeths, then you might wish to skip the first two questions.
Abdullaah was Umar's son
Abdullaah was Umar's father
They were half brothers, having the same mother
They were cousins
He could not think of any more hadeeths
This hadeeth is even more direct and clear in explaining that Islaam is built on five pillars
This topic is so important that it is worth repeating
It was an error on the part of the primitive printers
To show that the pillars can be listed in a different order
To emphasise the pillars of Islaam
The two testimonies are given here, whereas only the first testimony was given in the first hadeeth
The order of the Prayer and the Zakaah in the list are swopped around
The order of the Fasting and the Hajj in the list are swopped around
It is built of bricks
It protects its owner from the inside and outside
It protects the owner from the outside but not the inside
It shades its owner
Comes before the testimony, "laa ilaaha ill Allaah"
Is not as important as the other testimonysince a person can have complete belief without it
Is unconnected to worship
Is combined with the testimony, "laa ilaaha ill Allaah," into a single pillar
Here's an interesting quiz for you.