If public transport mapping is your goal, it might make sense to try out the MapComplete Train Station https://mapcomplete.org/stations and Bus Routes https://mapcomplete.org/transit themes which give an easier, more focused, mapping interface. Quest apps like Street Complete can also make getting into OSM a bit easier, though OSM Beginners Guise is great too. https://wiki.openstreetmap.org/wiki/Beginners%27_guide

Yes! https://wiki.openstreetmap.org/wiki/Public_transport though it is a bit complex to fully add routes, adding stops is super easy!

OSM doesn’t really track live and exact public transport schedules (you can define static routes and say which interval the tram/whatever comes but that’s about it). Organic Maps is working on implementing live data: https://github.com/organicmaps/organicmaps/issues/5331