4/ Different #OpenStreetMap communities (or people within those communities) use different tools and platforms to communicate.
Mailing lists are common https://lists.openstreetmap.org/listinfo, but some prefer IRC, Facebook, Telegram, forums, some are active here in the fediverse, etc. It really varies. The world is a diverse place
5/ Hereβs a wonderful world map run by @osm_be to click around on and see the local OpenStreetMap communities for an area:
https://community.osm.be
#OpenStreetMap