Punches to the back of the head are definitely not allowed but his land on the top of the forehead so I dont see the problem.
Murray showed great heart but was just a ko waiting to happen sitting on the ropes, the problem is when the other guy tastes Golovkins power they naturally back away and Golovkin is so good at cutting the ring down that before you know it your on the ropes anyway.
Loads of Golovkins opponents have said he puts you in places you dont wanna be with his footwork.

Golovkin really is unique and something very very special.

He turns his wrists inwards just before his punches land too which increases the power and accuracy which makes him a lethal body puncher.

Great great fighter and brilliant to watch.