Thanks for the feedback.
1. To play a song repeatedly, all you have to do is create a playlist with this one song and set the start mode as “No delay”. Alternatively you can also create loops within a song on the fly. When a song is playing, if you press the Settings button you can choose your start and end point with the rotary encoder. When the end point is chosen the loop automatically starts and plays until you press stop or back.
The playlist is definitely the way to go for galleries, because then it can be set as “autoplay playlist” to start playing it by just plugging in the device.
2. Unfortunately we never tested with a hard-drive with an ON button. We will have a look into this problem.
3. As point 2, we will look into this feature implementation too.
4. This one is a very strange issue which we have never encountered. The song is played until the complete length. Unless a loop is set in which case it plays until the end point of the loop. The best way to look for the problem would be to get your files so that we can test it. Could you upload the song to dropbox and send a link to firstname.lastname@example.org
Thanks again for taking the time to write such a detailed query. Hope we can help you before the Gallery reopens.