4.5 Does multiplayer work?
Before v0.5.0 beta 8, only the server would see connected cars. From v0.5.0 beta 8, things are a bit better; both sides should see and update the cars. Still not much more than that though. It may be that gameplay is still limited to one-to-one.
4.6 Does Internet multiplayer work?
For a good part, Internet play is similar to LAN multiplayer. Firewalls and bandwidth are the main concern, and I haven't investigated or experienced much in that direction. Whatever happens, a lot will be tweakable to be able to let Racer run on modem-speed connections.