I have upgraded from 4.1.2 to 4.3, and yesterday upgraded more recent version of 4.3 (I9300XXEMG4, I9300OXAGMK6, I9300XXUGNB4) but problem persists.
I edited /efs/carrier/HiddenMenu to contain ON and also tried adding the line to /system/build.props. Then shutdown and battery away. Still the codes won't work.
I have installed programs from Google Play to launch the menu programmatically, with no success whatsoever.
Any help would be highly appreciated.
Do I have to downgrade to 4.1.2?
PS. The bottom line reason for this is that the WLAN doesn't work because of the interference of another phone (S2+) and I would like to try and change the hidden properties and perhaps be able to use the WLAN with my phone.