"Note that running programs that access the network or mount/unmount filesystems is not allowed inside of udev rules, due to the default sandbox that is enforced on systemd-udevd.service."
I have not tested or looked into the specifics of the implementation to be able to answer your second question.
From the udev man page:
"Note that running programs that access the network or mount/unmount filesystems is not allowed inside of udev rules, due to the default sandbox that is enforced on systemd- udevd.service. "
I have not tested or looked into the specifics of the implementation to be able to answer your second question.