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This is a big news for BlackBerry 8520 owners like me who can install the Blackberry OS 5.X version which is release officially now. You can Download from BlackBerry.com
I had been using a cracked version since few months so I am sure there are not much of pie for me but if you still have 4.6 on your 8520 this is going to be awesome upgrade for you. However keep an eye on BlackBerry App world application to see if it works on Wifi because for me it did not on os 5, not sure if it was because of the cracked version or it needs BIS.