The * button is the Options button. Many times you'll see Options * in the upper right corner of the screen indicating that if you press the button you'll be presented with various options. If it appears dimmed instead of bright there are no options available. You can also press it while a video is playing to get to certain options.
The button with the counter-clockwise circular arrow is the Instant Replay button. It only has an effect while watching a video. It's supposed to jump back several seconds instantly, but it's often more frustrating to use than it's worth. Sometimes it works, sometimes it just locks things up for several seconds, sometimes it does nothing, and sometimes it jumps back way too far. I've found it's often better to just use the left pointing arrow button.
