Quick question about a booked RTW that I need to change...not totally clear on the way to describe it but I think it's an open jaw with a surface sector?

Original plan was as follows:
IAD-GVA (stopover)-FRA-PEK (stopover)-HKG(stopover)-IAD

The PEK stop has been replaced with a few days in Sanya (Hainan Island) and I'm wondering if I can change the ticket as follows and still keep a valid RTW routing:

IAD-GVA (stopover)-FRA-PEK (PEK-SYX-HKG on a non-star alliance carrier) HKG (stopover)-IAD (home)

PEK would still appear as a stopover
Transit between PEK and HKG would be surface sector (?)
Then staying in HKG for a week before flying home.

The other alternative is to simply route PEK-SYX-PEK and then fly to HKG but that adds several hours...

Is this valid?

Should be no problem, open jaws on almost all RTW's are permitted.
Is this a star RTW? I thought required minimum 5 stopovers?

I am presuming this is one of the mini-RTW Asia1 options? If so you can certainly do so, you are allowed one stop plus one openjaw because essentially this is still a 3 stop itinerary, you're just responsible for the travel in between two stops. Actually I would hazard a guess that you might even get refunded a small amount of taxes or fees! Could be wrong on that count though, but it would make sense.