1) you can manually do it or set it to do it automatically when you close a program.
2) the sandbox can pertain to any program. ie you can run any program sandboxed, from browsers, to email programs, to microsoft word. The main intent is to use it for internet facing programs,
3)works perfectly with other security software. I find it particularly useful when using file sharing programs like Limewire. Run them sandboxed, and if you download a file that is a virus, your antivirus will alert you. Then, delete the sandbox, and voilla, the virus is history! That sams scenario works well for email as well. If you're running your email program sandboxed or you use webmail, and get en email virus and your antivirus alerts you, just delete the sandbox and it's gone.