Apple still signs the OTA (Over-the-Air) manifest for iOS 6.1.3 for the 4S, making it one of the few devices that can be officially downgraded without "blobs."
A popular tweak that allows you to dual-boot two different versions of iOS on the same 4S. Technical Checklist for Installation proshivki aifon 4s skachat
Websites like are the industry standard. They pull direct links from Apple’s servers. Select "iPhone" -> "iPhone 4S". Green entries are "Signed" (can be installed via iTunes). Apple still signs the OTA (Over-the-Air) manifest for iOS 6
If you are looking to push the limits, the jailbreak community offers tools to modify your firmware. The primary jailbreak for iOS 9.3.6. proshivki aifon 4s skachat
The 30-pin connector must be high quality; cheap cables often fail during firmware writes. The Verdict