User Manual Ubiquiti UAP-AC-LR-US Unifi Ap-AC Long Range Wireless Access Point

This is an access point so it only does WIFI. You would probably need 4 to 8 of these to cover that much space. They are designed to work together and are centrally managed. They are also rock solid once they are configured.

It should be compatible with previous generation it didn't change much.

Mine came with everything needed for mounting and the poe supply.

Comes with a wall mounting piece (similar to the way a smoke alarm is mounted), or, the unit can simply sit on a table.

Yes, the Unifi controller is web based if you run it on a local server.

Yes you can install all three at the same time or separate.

The can be used with any switch or router with Ethernet ports.

The poe injector is just putting dc voltage on two wires, you can put it anywhere after the switch/ router.