1. How to query for all highways in Overpass API (demo: overpass-turbo.eu/s/3sB):

    <osm-script output="json">
      <query type="way" into="highways">
        <bbox-query {{bbox}}/>
        <has-kv k="highway" />
        <item set="highways"/>
        <recurse from="highways" type="down"/>
      <print mode="body" order="quadtile"/>

    This returns all highways without filtering, check out the OSM Highway docs for different possible types of highway, and add a v="" attribute to the has-kv element to filter.

  2. I finished off the Nominatim geocoding. Tack .json onto the end of this URL and have a look in the tags array for goodies. h-adr and h-geo coming soon.