The OS is not specific for each model. The OS works like OS 6 or OS 7 (thinks its currently OS 7 something). It's likely that the 9360 has either a newer or older software version. If older, it would simply need updating to the newer software. Not all blackberry's can get the newer software OS 7 though. Also, if the software is the newer version, I'm not sure if you can downgrade. in either situation, you might not be able to change the OS to the same as the 8520. Best to check which software each is running first then delve into it more. Hope this helps in some way