About 1,2,3,4 you can search yourself in the API and spec. It's a good exercice.
Concerning 5, it mays influence a few things. For example, the
servlets with a <load-at-startup> set the the same number will be loaded in the order they have been defined in web.xml. (But I think it depends on the container)
The way listeners and filters are loaded is also related to the order.