If you trying to find the guide on how to downgrade from iOS 9.3.4 to 9.3.3 it is not actual now as Apple has just closed the signing window the last jailbreakable version of iOS. It is nearly three weeks since iOS 9.3.4 was released to public to patched the exploits that was used by Pangu team to develop jailbreak for iOS 9.2- 9.3.3 devices.
Now Apple made it impossible to downgrade from the latest firmware version available to these older ones. So those users who accidently updated their device to the latest public software release and were hoping to downgrade from iOS 9.3.4 to 9.3.3 and jailbreak it now stuck at unjailbreakable version.
It is already known that Apple allows users to temporarily downgrade from the latest software version available to the previous one. The company typically leaves a two-week window between the time the latest software is released and the time the previous one stops being signed.
Of course for users who don't care about jailbreak this doesn’t really have any impact on the usage of their devices. However, for jailbreak users, this means that they should be extra careful not to accidentally update their devices to iOS 9.3.4, as there is now no going back.
As it was already mentioned iOS 9.3.4 was launched on August 4. This release didn't bring any new feature or some improvements. Apple pushed this update to patch exploits used by the Pangu Team in the release of their latest jailbreak for iOS 9.3.3 devices. Currently there is no jailbreak available to jailbreak iOS 9.3.4 version. iOS hacker Luca Todesco recently showed off a jailbroken iPhone running iOS 9.3.4, but as with all his previous jailbreak introductions we don't expect him to release this last to public. So if you stuck on iOS 9.3.4 and want to jailbreak it the only way is to wait till Pangu or other hackers team will push the jailbreak tool for this version.