Yep, this thing has a fan, you can see it in the UniFi Overview -> Fan Level. Like the larger 16 XG, it runs permanently. And yes, in a quiet environment you can hear it clearly.
Yes, the switch automatically detects the speed of the connected devices. It supports 1Gbit/s, 2.5Gbit/s, 5Gbit/s and 10Gbit/s. The speed of a port can be configured to fixed via configuration.
For the rack, the necessary sheet metal parts are missing to achieve a 19 inch installation width, but if you look at the side panels in the last photo, there are 4 screw holes on each side and the supplied accessories at least allow wall mounting.
Scope of delivery:
Mounting brackets, 8 screws, 4 x screws, 4 wall anchors.