X-Plane 11 or 12
Windows and macOS. Nothing else to install
Install the plugin and fly together
Sign up, take the archive from your account, drop the folder into plugins. X-Plane 11 and 12
A FLYWEE account
Free. The plugin is downloaded from your account
Two computers
Two pilots, each with their own X-Plane
The same aircraft
The same model and version on both — the plugin says so if not
Questions
No. The link runs through our servers
No. Only the one who invites pays; the friend joins with a code
Any: the plugin reads the cockpit itself, from a Cessna to ToLiss and the FF 777
You do not: a new version arrives between flights and switches in without restarting X-Plane