We have not tried it, but I do not see why the muscle sensor would not measure a finger movement if the electrodes were placed correctly. We have also not tried using things other than the included hardware as electrodes, so we are not sure if other materials might possibly work with it.
I recommend contacting the manufacturer, Advancer Technologies, to get more definitive answers to those questions and to learn more about the ICs that they use on the muscle sensor.
While the LCD pins on the A-Star Prime are remappable, it's probably not that practical to use it on the Zumo with an LCD. However, we are currently working on a Zumo version with built-in LCD support, so stay tuned!
I am sorry you are having trouble using the DRV8838 motor driver. It is difficult to tell what might be the issue without additional information, and this comment section is not very well suited for troubleshooting. Can you post a more detailed description of your setup including pictures of all your connections on our forum?
I am sorry you are having trouble using the P*. However, the blog is not an appropriate place for troubleshooting your problem. Instead, you might post this on our forum with more details about your setup.