Does cocos2dx 3.0 use Right-handed coordinates just as OpenGL?
If yes, why the sprite rotates clockwise?
Yep, cocos2d-x uses right-handed coordinates. rotation direction uses clockwise is a history from cocos2d-iphone. I thin you are the first one that point out it, but can not change it in v3.x, may change it in v4.
We talk about this in our docs: http://cocos2d-x.org/docs/cocos2d-x/en/scenes/creating.html?h=coordinate
This is good. All cocos project that I have used surely have a utility method to convert the angles. Didnt really point that out because it doesnt sound like a bug. I thought the cocos team purposely do it this way for some reason. =D