the powerline receiver is connected to your computer directly? how would that affect your wireless keyboard and mouse? it's a bit confused. Or the receiver plugs into the keyboard with Ethernet?

based on that error message, that's how the router is designed. it will not affect your profile settings anyway, what's important is the info provided by ISP

you are not gonna use a SIM card? as I know the antennas on the router are 4G LTE antennas. 4G signal is mainly depended on your ISP and the sim card. antenna type is SMA male. you can change the...

you can check whether your dongle is on the compatibility list. it's on it or not, you can update the settings. http://uk.tp-link.com/faq-269.html

you can check if both printers and apple devices are connected to the same network.(login router web management page---DHCP--DHCP client list) what error message comes up when you try to print?

it should not be a problem with 2.4ghz connection. you can connect those devices to 5ghz and see if they can use DLNA, if no, then it is those devices not the 2.4ghz issue.