Sure! So you cannot reach it in 3D at first. Think of a way you might be able to access that room in 2D. Hint: is there somewhere else you can leave the key in 3D, that it can be found in 2D? Then, if you get the axe in 2D, ask the same question: is there somewhere else you can leave the axe in 2D, that it can be found in 3D? Let me know if you need another hint :)