If you've installed a new launcher, when you press the home button for the first time, it will ask you which launcher would you like and set it default or not. Default launcher also can be changed in settings.
You can flash the Chinese firmware with wiping the data first. When the flashing done, go to settings, format internal storage, then you can login your own account
yep I did. I turned on the wifi in setting or notification bar but actually it was not on, the phone didn't scan any wifi network. And I went back and go into the wifi setting again, the wifi was off.
And I flashed twice ( both wiped everything ) but the problem was still.