A server is just some computer somewhere that other machines can connect to. You can get specialised hardware and network setups and other technical stuff, but you can also just use your personal laptop as a server by allowing people to connect to it. A server essentially boils down to someone leaving their computer on.
Wifi is just radio waves. You can think of it like people talking on a two-way radio, except instead of humans speaking it’s computers.
Doesn’t he? After essentially destroying the cure he freezes himself so he can survive.