Oh wow, so many posts since last I checked the thread.
Not too sure if you folks already know about the LG "(secret) service menu" but for those who don't, here is the code for our variant -
277634#*#
As for those who want to check the screen for "dead-pixels" you can conduct the following test -
Go to your phone dialer and key in > 277634#*# > Device Test > SAAT > Service Menu > Manual Test > Display Check Test
The above test does NOT require any network/sim/wifi connection so before you walk out of the store with a G4, do the above check if convenient.
Also on the side note, "service menu" as implied is meant for LG service staff to conduct quick test(s). Though, I doubt anyone will give a diddly about that but please tinker at your own risk with the other options within this menu.
And if you find something sweet, PLEASE share..