Currently, iOS 8.4.1 yesterday released is the latest system for iPhone, iPad and iPod touch, new version includes several bug fixes and improvements for Apple Music, while it also blocked the TaiG iOS 8.4 jailbreak by patching several exploits used by the jailbreak tool, but the good news is that Apple not yet stop signing the iOS 8.4 firmware, which means you can now downgrade your device back to 8.4 from 8.4.1 to regain the jailbreak.
So now if you regret the wrong upgrade, and want to back to iOS 8.4, then follow the below tutorial to downgrade your device.
You should backup the data of your iOS device using iCloud or iTunes to prevent unknown risks.
Step 1: Put your device in DFU mode.
Step 2: Plug your device into your computer.
Step 3: Once the iTunes detected that your device is in Recovery mode, click on the Restore iPhone… (iPad/iPod touch…) button.
Step 4: Then click on the Restore and Update button to continue.
Step 5: In the next screen, it will give you information about the iOS 8.4 update. Click on the Next button, followed by the Agree button to continue.
Step 6: iTunes will now download the iOS 8.4 software and install it on your device. It should take around 10 minutes.
Step 7: After it is successfully restored to iOS 8.4, you should see the white ‘Helo’ screen. Follow the on-screen instructions to set up your device, and restore your device from the backup to restore your personal data.
Step 1: Turn off Find my iPhone via the Settings app (Settings > iCloud > Find my iPhone).
Step 2: Download the appropriate iOS 8.4 firmware file from our download page for your iPhone, iPad or iPod touch.
Step 3: Connect your iPhone to computer.
Step 4: Launch iTunes and select the iOS device from the top right corner, to the left of the iTunes Store button.
Hold the Alt/Option key on the Mac or Shift Key in Windows on your keyboard and click on the Check for Update option, instead of restoring.
Important note: We were able to successfully downgrade from iOS 8.4.1 to iOS 8.4 using this step, but if you want to go by the book then you should use the Restore method, but it will be more time-consuming. If you use the Restore method, then it will wipe the data from your device so please don’t forget to take a backup.
Step 5: Select the ipsw file you had downloaded earlier. Then iTunes will inform that it will update your iOS device to iOS 8.4 and will verify the update with Apple.
Step 6: Click Update.
iTunes should now downgrade your iOS device to iOS 8.4.
After downgrading, the iOS device will restart. You should then see “Slide to upgrade”. Enter the passcode, and then wait for the downgrade process to complete. You may be prompted to activate your device.
That’s it. Your iPhone or iPad should now be successfully downgraded to iOS 8.4.