ok, after days of searching for answer, i believe i've figured it out, sadly from other game dev software's forum...
the event is pretty straight forward, how i did as mentioned above was correct, testing in adhoc part was tricky! you need to log out of your gamecenter first before launching adhoc version of the app you want to test.
if you did not log out in first place, gamecenter could play up, like i experienced before, it may not log in or cant connect to server or all sorts of strange error message.
and the worst is ios7 disable your app's gamecenter feature, this happen after 3~5 failed attempt to login, you simply stop getting any gamecenter response, no login box, nothing(this can be misleading to bad event coding), and with ios7 you cant re-enable gamecenter for your app(stupid i know).
the solution is go to general>rest>reset all settings
it will wipe out all your settings on your device, data remain on device.
after that you can test your app again with gamecenter.
go to your adhoc app, gamecenter will pop up and ask you to login, use your login, and it will ask for more info like register a new ID, continue with that because its creating a sandbox account for you, once thats set up, you should be in sandbox mode gamecenter :)
hope that helps, and i hope there are some proper documentation on cocoonjs plugin, i have a feeling i have to go through this again when i need IAP and other feature :/