*** Successfully Installed Opera Mini beta (ver 23.0.2254.114097 , latest) in to my phone (Moto E , Android 4.4.4) :happy:
The issue earlier for not installing was due to "write" permission denied for External SD card by Android system. Earlier versions of Opera mini beta (ver 22) was moved to External SD card by me. When i tried to install latest opera mini beta ver 23 , by the time, Android system denied write permission to External SD card (as Google play store trying to install latest opera mini beta 23 app directly to external SD card). Hence, i removed External SD card and successfully installed opera mini beta ver 23 (This time it was installed directly in to local SD memory). Then, put back External SD card. Launched opera mini beta ver 23 , it is working fine now.
For reference: The issue with External SD card "write" permission is mentioned in the following link,