No, externals cannot be included unless they are built into the project at compile-time (i.e. from the source). The public versions of MobMuPlat are currently vanilla-only.
(Note that the "built-in" externals, fiddle~, etc, are available).
Yes, see the "MMPExamples-Networking.mmp" example, which takes slider touch and sends out an OSC network message. Go to the MobMuPlat Network settings to specify a destination IP address and port number.
Then have your computer listen on that port (using UDP). In pd on your computer, that would be
[ listen XXXXX (
[netreceive -u -b]
(but if you look at PdWrapper.pd, you'll see my custom solution for getting the OSC messages in a preferable format (with the slashes intact) rather than what [oscparse] does)