iTunes is not forward compatible with iOS devices, regardless of the version. In other words, an outdated version of iTunes will not allow you to backup or restore your iOS devices. Because of backward compatibility, older iOS versions can work with newer iTunes versions. iTunes may fix a faulty version of iOS, it must have the current version's code as well as enough relevant code for previous versions. However, every time you connect your iOS device to iTunes, you will be prompted to update your iOS