When it arrives iOS 8.4 is going to bring with it lots of new features, however it will not be for everyone. The good news is that if you install the OS and you then want to downgrade, you can very easily. You can go back to iOS 7.1 or any other OS you want through iTunes. So how do you do it?
The first step to downgrading from iOS 8.4 if you find you don’t like it is to connect your phone to your computer and then open up iTunes.
You should then boot your iPhone into DFU and you can press the Home and Power buttons to do this for around 10 seconds. Release the Power button and iTunes will then know that your device is in recovery.
You then have to hold down shift on your keyboard or in the case of Mac Alt/Option key and then choose restore on iTunes.
You can then pick the files that you downloaded earlier and the installation with begin and complete.
You should now have downgraded from iOS 8.4 to the OS of your choice.