There's a few buttons at the top, Mode 1, Mode 2 and Mode 3; and Controls 1 and Controls 2.
Mode 1 and Controls 1 is the default. Controls1 click and drag moves like first person camera, controls 2 , click and move is an obit camera (not really important; no motion really required)
Mode 1 - top left cube is reference relative rotation cube stepping through each of the variations... The bottom 6 cubes have their relative rotation always applied in the same order (the order specified by the text over them) ... The 3 cubes above the bottom 6 are single rotation references for directionality... It turns 90 degress and then pauses. Mode 2 is the same as Mode 1 really except slightly faster; so the divergences appear sooner...
Mode 1 - the lower 6 are slow motion, as if rotated sequentailly 90 degrees in each of it's directions; in the various combinartions. THe three rotations happen then a pause showing completed doing 90 degrees each way.
Mode2 - always applies the rotations in the same order but in smaller steps; some of these are faster than the ideal (top left) and some are slower.... I'm not sure what the reason exactly is for the combinations of three that are the same.
Mode 3 the lower 6 cubes are based on building a quaternion using roll pitch yaw... multiplying in order (if text is yaw, pitch, roll... the multiplication is ( ( yaw * pitch ) * roll ) . This is saved as a target vector, and then a slerp is used between initial position and the computed target... so especially with larger angles applied; the resulting computation is not the same... demonstrating quaternions to have similar problems... and ideally should also be muxed though an iteration of applied ordering.