I have an unlocked BB 7780, and I wanted to upgrade the OS. I want to know if there is any specific restrictions or paths that I need to take in order to upgrade its software.
What OS version do you currently have? Options/about 3rd line down. I believe 4.0.2.56 is the newest version for that device. I havent seen one of these 7700's in a while. I used to have one a long time ago. You might want to look into getting an 8700 series phone. It is a more recent device and supports 4.5 OS.
To update the OS, goto the website of the carrier who the phone is branded to. Then in their Blackberry OS update site, choose your model number and see if there is a OS with a newer build than the one currently installed on your blackberry