Earlier today Apple released what would quickly be revealed to be an extremely broken update for iOS 8 that resulted in a complete loss of cellular connectivity and Touch ID support on its newest line of iPhones. Now, nearly twelve hours after the update went live, the company has published a new help document for users stranded on the faulty operating system.
The document lists the steps for restoring a device back to iOS 8.0 with links to download the appropriate IPSW file. Interestingly, the page notes that the Health application will stop working, likely due to changes that were made in 8.0.1 and cannot be reverted to work on the older firmware. The notice also points out that it is crucial to back up your device in the iTunes app for Mac or PC rather than to iCloud, as iCloud-based backups will not restore to the older version.

Apple also notes that an update ,version 8.0.2 is currently in the works and will be available “in the next few days ,”hopefully with a few more rounds of testing IOS 8.0.1 went through
http://.com/apple-ios-8-downgrade-instruction/