Downgrading your iPhone Firmware is very easy and you can do it on your own through the internet and by using the TinyUmbrella (Mac). There are proper steps and stages of doing so and if you follow these then no problem will arise for you in meeting your goal. But one thing to mind here is that before starting to follow these, you will first have to save your SHSH Blobs for the firmware to which you want to downgrade your phone. It is actually to downgrade to the iOS 4.3.3 firmware for which you can take help of this tutorial and for this you will have to use JailbreakMe.
Check out and follow the steps below:
1. Firstly, you have to start with downloading and installing TinyUmbrella.
2. Secondly, you will have to download the firmware to which you want to restore your iPhone and keep it saved in your desktop.
3. The next step would be to launch TinyUmbrella from that you already have kept saved in your Applications folder.
4. Now start connecting your device and see that the SHSH Blobs you have kept saved is listed by the device for the firmware. However, if you cannot find any blobs then you can save it again by clicking on the Save SHSH button and load it from Cydia.
5. After all these you can now click on the Start TSS Server button. However, you will also have to see that the TinyUmbrella’s TSS server have started successfully.
6. It is now the turn of launching the iTunes by clicking on its icon found in the dock.
7. After launching the iTune, the iPhone will have to be placed into DFU mode for which the by Power and Home buttons will need to be hold down for 10 seconds. After the said duration, the Power button should be released but the Home button should be continued to hold for another 10 seconds.
8. This will be followed by selecting the iPhone from the list of devices given on the left. Now press down the Option key and click on Restore.
9. Now it is time that you go to the Pwnage folder on the desktop where you have kept the firmware saved and select the ipsw file that you have downloaded and open it by clicking on the Open button.
10. The iTunes will now get restored to the lower firmware version.
11. While restoring to the firmware, if you happen to find Error 1 or get stuck somewhere in the recovery mode, FixRecovery can be used to get out of this state.
12. Now repeat the same steps of keeping the iPhone into DFU mode that you have already done in the seventh step.
13. Click twice on the fixrecovery43 to launch it from the fixrecovery-osx folder and once it is done; you will successfully finish rebooting your iPhone.