Not strictly the correct reassembly method - the final step is that the backplate just under the camera and LED flash must be pressed for the final clip to be set, to ensure a complete water seal within the rear cover.

I think the orange circle refers to a 4th gate connector which needs to be disconnected.

What does the orange circle refer to, as the text is a duplicate of the red circle description (and the highlighted item isn't connected with the three gate connectors)?

The orange circle in line with the 4 other red circles down the RH side (as shown) in the photo should be red also, as this shows a screw, not the cable (which is by the volume buttons).