Open Jaw is flying A to B and then C to A on the return.

Stop over is just Flying A to B to C to A with the time spent in B greater than the allowed layover time for your fare rules.

You can mix carriers on an award ticket, IF you can find availability. (search here for starnet blocking and the many problems of finding XC to Asia.)

You are doing a stop over, not an open jaw - can't help you on validity (your routing is valid, but don't know if it is allowed on an award ticket).