The correct answer is the third cover.
This inside back cover of a magazine is known as the third cover in the publishing industry. First cover is in the front, second cover in the back, and the third cover inside the magazine's last page. Bleed refers to the printing beyond the edge of where the paper is supposed to be trimmed. Gatefold is the paper that is folded and supposed to be unfolded if you want to see the entire thing.
