#2 What do they mean “large four thirds”? how does that compare in size to full frame, aps-c and micro four thirds?
4/3 and micro 4/3 are the same size lens. Full Fram lens doesn't apply concerning this camera. The lens as a 4/2 lens. To learn how a full frame differs from a 4/3, just use google and type in "4/3 lens vs full frame". Full frame is the lasrgest sized lens possible on today's cameras. APC lens are next in size and 4/3 or micro 4/3 (same size) is just a bit smaller than APC. APC cameras can also use 4/3 lens, just doesn't use all the app features.