Doubtful many will read through steps beforehand to complete the tear down, but the rotation isn’t necessary. Back panel can be removed keeping the printer horizontal. In the next step, if this screw is removed at the beginning, parts will simply drop out if you lift printer up vertically (or might need a little help from you). No need to worry about the loose feed roller assembly.

Perhaps my model is slightly different, but I never saw any ‘plastic grey square clamps’. The two tabs seen in the picture are metal, part of the backing but not coloured. They may have been what I was supposed to press, but my backing was almost glued down with dirt. I removed it eventually by starting at a corner and slowly prying, working back and forth between all the corners until one finally released.