You may do it with some other routers such as WR841N, or Archer C7. You can set the white list rule, host 192.168.0.2--192.168.0.254, target IP opendns sever, port 53....

tplink router cannot handle hostname. but windows pc supports LLMNR, so you can ping hostname between windows pcs.

Is the WiFi light still lit up? So with that error code 1, you cannot turn WiFi on via the web interface? Usually it's turned on by default. If the WiFi light is not on, you may press the WiFi button...

Yes if tplink put a firmware on the regional website even though the firmware displays other region, you can upgrade it. But the current firmware version needs to be US version or a UN.

What is PPPoE passthrough? Do you mean to set the modem in bridge mode and dial up on your computer?

If the store declined your warranty claim, contact the tplink support