is updated to its maximum firmware (iOS 9.3.5/9.3.6), it is recommended to use at least for full compatibility.
You can find the official installers on the page. iPhone 4S - Technical Specifications - Apple Support skachat itunes dlia 4s na kompiuter
System Requirements * Apple ID (required for some features) * Internet access5 * Syncing with iTunes on a Mac or PC requires: Mac: Apple Support is updated to its maximum firmware (iOS 9