This plugin can be used to connect to another wordpress blog located in a subdomain on the same server. It provides various ways to display posts.
Yes. In this version there is no seup for the widget. It is configured in the main plugins setup
Yes. The short codes use only the database connection options from the main setup. The rest of the parameters can be different and they are defined in the short code
No. The plugin does not use any CSS of its own. Just keep in mind that when you display a full post from another blog the look may be different from the original. There is a class connect2site for custom CSS, otherwise the plugin uses the CSS properties of your theme.