Yes - they can contact the council - information is at https://www.ardsandnorthdown.gov.uk/resident/public-rights-of-way, with an email address above the download links near the bottom of the page. I added all the PROWs in the council area to OSM around the time of this changeset, based on information I got from the council, so the legal status is correct as of a few months ago.

Yes - it's designated as a public footpath by Ards and North Down Borough Council. I haven't checked it's existence on the ground, but it is a public right of way by law.