The process will wipe your device. Backups from newer iOS versions (like iOS 10) cannot be restored to iOS 8. Turn off "Find My iPhone": Disable this in Settings > [Your Name] > Find My to avoid activation locks. Computer Access: You will need a Mac or PC to run the necessary tools. Microsoft Community Hub Method 1: The "OTA Trick" (Recommended for Beginners)
Even with this method, due to baseband mismatch. Many report success for WiFi-only functionality, but cellular + GPS will likely fail. downgrade iphone 5 to ios 8