Volumes Support

Volumes are network-based block devices that provide additional data storage for Droplets. You can move them between Droplets, create disk images of them, and resize them at any time.

No, but you can mount a remote filesystem on a Droplet with the volume attached using software like SSHFS or NFS.
Adding a volume to your Droplet doesn’t increase its main disk size. You need to resize the Droplet to increase its main disk size.
Filesystem tools often don’t report the capacity reserved for metadata and the root user, and some report size in different units.