TP-Link ‎TL-SG108PE V3 | 8 Port Gigabit PoE Switch

PoE stands for Power over Ethernet. PoE is an industry standard for networking infrastructure, allowing PoE compatible devices to receive both power and Ethernet network connectivity via the RJ45 (Ethernet) cable.

I don't see why not. There is no ventilation holes on the top or bottom. Vent holes are on the sides. network cables plug in the front and power cord back.

Yes, it will work as a regular gigabit port if the device doesn’t require POE.

If you have a 1gbps internet plan then you'll be able to get almost 1gbps combined to all of your devices. The switch provides full 1gbps to every port simultaneously so you can communicate between two local devices at full 1gbps as well as to the internet at 1gbps but you can't get more than 1gbps from the internet port.

No, it is designed as a desktop style switch or wall mountable. It is less than 1U in height and far too narrow for rack ears to reach

A switch has nothing to do with setting up a guest network on as access point