If you're still one of the few using an iPhone 5, you better heed the full-screen alerts your device is getting that remind you to update to the latest available software. Apple is telling these users that they will use access to critical online features if they don't update to iOS 10.3.4 before 12 a.m. UTC on November 3rd. You will not be able to access essential apps and services like email, web browsing, iCloud, and the App Store. You will not be left entirely with an almost useless smartphone if you're unable to update by that date, though. But you will need to backup and restore to a computer through iTunes.
The update fixes a GPS time rollover issue that began in April, and it affects other older devices like the fourth-generation iPad. But those devices only lose GPS functionality. Only the iPhone 5 has a more significant issue.
Source: Engadget