M8, its some real basics. If you cant answer any of those questions, I think you need to read more.
Here is help with one.
Air is diverging in upper part (going away from each other).
This "creates" an "empty space", that have to be filled with new air.
So air from the ground starts to rise to fill this gap.
When air rises, it get cooled down. Drop in temp - higher relative humidity, condensation, clouds start to form.
So answer is rising of the air and formation of the clouds.
Read this at least. This will help you with other questions as well.
Low-pressure area - Wikipedia, the free encyclopedia