On 2, the door is expanding because things expand when they heat. Think about it: when you boil water, it's kinetic energy increases, moves about more (takes up more space), and turns to steam.
For 3, think of things similar to 2. Window panes, bridges maybe...
4 is pretty much the same as 3. Just come up with things in your daily life.
On 5, I couldn't see the whole question but I think you would fill it up with less air than you would in cold areas. This is because when things get hot, they expand. If you filled up the mattress all the way and the air expanded, it would pop. Not good.
