I can answer a couple of these, but not the touchscreen one :
2) You can disable the user(s) from being able to duplicate a song in the queue, but only if the song is still in the queue. So, if the 'duck dance' finished a couple of minutes ago, there's nothing currently stopping them from queuing it up again (apart from not having it on there in the 1st place
).
3) This should be pretty easy. Just make sure you're displaying the program full screen, and disable any keys you do not want the user(s) to access (by going into Key Remapping & right click on the key setting). If you disable the options key, you should be able to get back in there later to reset the keys to default by going holding Shift + Ctrl + Alt + O. This will force the program to go into the Options screen, even if you have the options key disabled.
Or, if you disable the options screen all together (rather than just the key), you will have to open the .ini file in a text editor & change the option back again.