So, if you’re still running iOS 10.3.3 or earlier on your iPhone and iPad and want to do so until iOS 11 is fine tuned in the upcoming months, don’t accidentally push that Download and Install button available on the Software Update screen, because once you upgrade to iOS 11.0.2, there is no way back to iOS 10.
How To Check Which iOS Versions Are Signed
Tap here to open the ipsw.me webpage and check what iOS versions are signed for your iPhone, iPad and iPod touch. Choose your device and select the specific model. A list with the signed firmware versions currently available, as well as their ISPW download links are provided.
Fact: iOS 11.0 was released on September 19 and Apple stopped signing it today, October 4. That’s only 15 days of signing for the initial version of the 11th iOS generation!