To start .. good choice to not start it. You should only start it or even have it hooked up to power after someone at Genius Bar gives an all clear.
You did not say if anyone reported pops or fizzles or if the unit was running and shut itself down.
If you are close to a Genius Bar, I would have them perform checks and let *them* open the unit.
Not sure what to say about having it verified.
I wish I knew of "service options" in China.
But although "posting twice" is discouraged, posting something new titled "Where to get iMac verified by Apple-certified people in China?" is I think reasonable because it will get the right attention due to the title.