The number keys work in conjunction with the T (tool) key and also if you right click and leave the menu up the numbers work as indicated. Numbers 1 to 4 above the keyboard are used to call screen presets. Your keyboard shortcuts are not standard, S does nothing here, so see what your tool command is.
Control M mutes anything but tracks. They changed to that because if you have selected a track and a region on a different track, your key command will always do what you expect and you don't have to remember what you selected last.