Android applications data usage (android experts preferred)?

[Ash]

Does anyone know about android application data usage? I am new to android and have gotten very concern about its applications using up data that I'm not aware of.

(1)-Do applications downloaded from android market use up data after they have been downloaded, such as live wallpaper?

(2) In the "manage applications" section, do the "running" are applications using data? Under the application, there is a number such as 36.00KB. Is that just how big it is or is is using that much data because it is running?

(3) Do widgets, like Daily Briefing, use up data while on they are on the home page since it tells you things like the weather?

(4) Is there a way to stop applications from running automatically? Everytime I force close an application, it comes back up there.

I know this is a lot, but I would really appreciate any information that can help me. Also, if there is any tips and tricks to keep data and personal info private, that would be great. Thanks in advance.