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.
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." proshivki aifon 4s skachat
Red entries are "Unsigned" (requires special tools like Legacy-iOS-Kit). 2. Custom Firmware & Jailbreaking If you are looking to push the limits,
Necessary for the restore process.
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