Clearly ramps were used up to a certain course level. The archaeological evidence is solid. Heck you can see a ramp out of the quarry so obviously stones were dragged up on it.
Yes, yes, yes. Common since, simple logic. I have seen the ramps up and out of the quarry. The indentation of slit logs, ground discoloring due to decay, is apparent.
These are not the kind of ramps I was bitching about. For all I know, they could have been disability ramps, leading into those structures. A promenade entrance? OK, they also served to help build the structures. There is evidence of ramps. Just not for G1 and G2. There was a downhill ramp/path reaching the backside of Kufu's Pyramid. They took block from what is known as the chocolate quarry, next to Kafreys Pyramid.
Other than that, I have seen no evidence ramps were used in a spiral or switchback fashion.