User IP - Simply display visitor IP Address on post or page with a shortcode.
Yes, of course.
Intall it. Activate it. Then use this shortcode in your page or post :
Yes, it works in a "text widget" with this same shortcode [user_ip].
There is no settings.
No, you can't. This plugin only show user IP Address. To display Server IP Address, use this WordPress plugin : http://wordpress.org/plugins/server-ip/
If you like "User IP" plugin, you can donate : http://adresseip.vpndock.com/wordpress-user-ip-address-plugin/