I was thinking that only the top two would be planar because the top left one clearly does not have any crossing edges and the diagonals of the one on the top right can be looped around. The one on the bottom left is clearly not planar because it is $K5$. However, I am not sure about the one on the bottom right. I thought that it was $K6$ and, therefore, also not planar but when I searched up for images of $K6$ it had more edges than the graph on the bottom right, leading me to think that the graph shown actually is planar.
So I just wanted to verify the thoughts I already have and am seeking some clarification for the graph on the bottom right.
Any help?
You can draw some of the edges as drawn in red color so I think a picture would explain everything.