I have been looking over the /user/share/X11/xkb/share/us file and have a few questions.

For the USA - ClassmatePC (International) layout the creator used the RCtrl key since the keyboard he was using didn’t have an AltGr key. However all he did was enter “include "level3(switch)"” in place of “include "level3(ralt_switch)"”. How does the system know to use RCtrl when all it says is “switch”?

I also prefer not using AltGr since my keyboard has no AltGr key and I would rather have the flexibility to use either Alt key by substituting Ctrl+Alt for the RAlt/AltGr key. Does leaving out “include "level3(ralt_switch)"” do this?

When I*used Microsoft Keyboard Layout Creator, it allowed me to use six levels by including Ctrl and Ctrl+Shft. From what I could see, there was two more levels I could have used theoretically by adding Alt and Alt+Shft to the Shift State and the two corresponding columns in the text file manually. Can X11 do this or am I*limited to a maximum of five levels?