Apple opened up its servers for users to download the new software, iOS 7, on Wednesday, September 19, 2013. The latest software version is is compatible with iPhone 4 and iPad 2 tablets and later versions.
Apple added new security features in IOS 7, so it will affect all devices using IOS 7. It was put in place for a theft deterrent, but also improves security of your device. An Apple ID and password is needed to activate a device, even after a rest, so stolen phones and even sold second party phones will not be able to be activated unless the previous owner deactivates properly or goes into iCloud and removes the device.