Inserts an image from a page you link to at the start of your blog post. A simple algorithm tries to get a "main content" image, not an ad.
No; this plugin uses WordPress filters to make changes on-the-fly. It does not change the content of your posts in any way, and it uninstalls cleanly, without leaving a trace. :)
No, not at this time, but I'm hoping to add this optional capability to future versions of the plugin. (Patches welcome.)