Well here are the answers for round 4 gold challenge.

11.

Far right clown missing nose on face
bottom right flowers is missing the red center
The hat of the first clown is different
There is a rung missingin the ladder in the background.
The flames in the bottom left are different
there is a spec of yellow missing above the flames in the bottom right corner.
There is a piece of grafiti missing in the white patch under the first clown.

12.

Alfred Hitchcock

Gold Challenge

Horn

the entertainer