Firstly, this only works, if you saved blobs (shsh) when you originally Jailbroke on 4.3.3. Trust me, I know a hell of a lot about Jailbreaking the the iPhone 4.

iPhone 4 only (slightly different Sn0wbreeze for 3GS)

What you will need is previously saved shsh (Cydia asks you the first time to save blobs - 'The make my life easier button), when you go into into Cydia, it lists all the possible iOS versions you have blobs for). If you can't remember, then try this anyway....

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What you need - Ingredients - For Both Methods (Be prepared )

1. Download Tiny Umbrella from - http://thefirmwareumbrella.blogspot.com/

2. Download Fix Recovery from - http://thefirmwareumbrella.blogspot.com/

3. Download zlib1.dll from - http://www.dll-files.com/zlib1.zip?0WDiS0aEmV

4. Download iOS 4.3.3 from - http://appldnld.apple.com/iPhone4/041-1011.20110503.q7fGc/iPhone3,1_4.3.3_8J2_Restore.ipsw

5. Make sure you have the latest iTunes from - https://www.apple.com/itunes/

6. Download Sn0wbreeze v2.7.3 from http://ih8sn0w.com/

7. Not needed,  as its within Sn0wbreeze, but hey... iReb from http://ih8sn0w.com/

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When you have the ingredients;

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Method 1 - Using standard default iOS 4.3.3

1. Start Tiny Umbrella. If you have any blobs (shsh) saved, it will tell you, go to the Log tab.

You need to have Java installed for it to work, but most people do, that's why its not on the ingredients list.



As you can see from the image, it says Tiny Umbrella's TSS server is NOT running. Click the "Start TSS Server" button. You may need to disable your firewall for it to work. You should now see the below image.



2. Put phone into DFU mode (black screen) whilst the iPhone is ON; by holding both the Home Button and the Sleep Button, let go of the Sleep Button when the screen goes blank, continue to hold the Home Button for another 5-10 seconds.

Tiny Umbrella will see it in the Log tab, if you open it up. You should have a blank/black screen. If you have trouble doing this, there are apps that can do this for you (Recboot and others).

3. Open iTunes, it should immediately tell you it has recognised a iPhone in Recovery mode. This is good

4. Now on your PC keyboard, hold down the "SHIFT" key and click "Restore" in iTunes, so you get this image, then navigate to where you downloaded the 4.3.3 software (see image). The firmware, should be in IPSW format!



5. iTunes, will extract the firmware, and then verify it. You can get a potential error, but you shouldn't, unless you have been playing with this before

6. When the restore has finished, you will get a 1016 error (or similar), and be stuck in a Recovery loop, with the iTunes logo on your iPhone screen. Now you need to load up "Fix Recovery". When you extract Fix Recovery, place the zlib1.dll in the folder (directory).

7. Open Fix Recovery, with your iPhone still connected of course. You will see some code start on your iPhone. Don't worry, this is normal.....

8. Your iPhone should reboot as normal, with 4.3.3 installed.

9. On your iPhone (unplug from PC now), open safari and go to http:www.jailbreakme.com and tap the buttons.....



10. JOB DONE

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If your iPhone does not get the iTunes recovery loop, yet stays on a black screen, then you have just BRICKED your iPhone...JOKE!!!!! PLEASE READ THE RESTORE BACK TO 4.3.5 BELOW[/b]

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Method 2 - Using custom firmware

1. Open Tiny Umbrella and start TSS server and then open up Snowbreeze 2.7.3, to get this image:



2. Drag your 4.3.3 IPSW firmware into the Sn0wbreeze window. Wait for Sn0wbreeze to verify the IPSW:



3. Click the Next button once the correct iDevice has been recognised:



4. Now select your options, see images below...choose whichever is applicable to you...if you have no idea what you are doing, then just select the SIMPLE mode:



5. Then select the General button, all these options are OPTIONAL! Pick what you want, then click NEXT.



6. Wait whilst Sn0wbreeze makes your cooks your new firmware.......

http://cdn.jaxov.com/wp-content/uploads/2011/05/Sn0wbreeze-2.7-Creating-IPSW.jpg

7. When it's done the custom IPSW will now be on your desktop.

http://cdn.jaxov.com/wp-content/uploads/2011/05/Sn0wbreeze-2.7-Done.jpg

8. Put phone into DFU mode (black screen) whilst the iPhone is ON; by holding both the Home Button and the Sleep Button, let go of the Sleep Button when the screen goes blank (around 10 seconds), continue to hold the Home Button for another 5-10 seconds.

Tiny Umbrella will see it in the Log tab, if you open it up. You should have a blank/black screen. If you have trouble doing this, there are apps that can do this for you (Recboot and others).

9. Sn0wbreeze will detect the iPhone in DFU mode and immediately put in in a 'pwned DFU  stated'.





10. Close Sn0wbreeze once iPhone has been 'pwned DFU'. Open iTunes, it should immediately tell you it has recognised a iPhone in Recovery mode. This is good

11.  Now on your PC keyboard, hold down the "SHIFT" key and click "Restore" in iTunes, select the 4.3.3 custom firmware from your desktop that you just created with Sn0wbreeze.

12. iTunes, will extract the firmware, and then verify it, then proceed to install 4.3.3 to your iPhone. When it is finished, your iPhone will boot and you will have a Jailbroken iPhone.

13. Job Done

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Restore Back to 4.3.5 - The quick and error free way!!

It will be a case that you didn't save your blobs (shsh) when you first used Cydia, and you iPhone is just dead in appearance, black screen.

You will now have to download 4.3.5 and restore from that, but to do that you will need to do the following.....

1. Download 4.3.5 from - http://appldnld.apple.com/iPhone4/041-1966.20110721.V3Ufe/iPhone3,1_4.3.5_8L1_Restore.ipsw

2. Stop Tiny Umbrella TSS server, and close the app (if you have it running).

3. Go to C:\Windows\System32\drivers\etc on your PC and delete the "HOSTS" file. Trust me!!

4. Open iTunes, and do the same as before, hold "SHIFT" on your PC keyboard, and click "Restore" in iTunes. Point it to the 4.3.5 firmware you just downloaded.

5. Job Done

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All links are in my post, just read it, from start to finish.

In fact, before you start, delete your hosts file (which is here C:\Windows\System32\drivers\etc).

If you can see 4.3.3 blobs, then you are fine. The iTunes recovery loop is easy to get out with Fix Recovery, which is listed in my ingredients in my reply (YOU NEED ZLIB1.DLL FOR IT TO WORK - in the same directory).

All you need to do is, follow my guide, step by step, and begin by deleting your current hosts file. Tiny Umbrella edits the hosts file for you.

You must have previously saved blobs, if you can see them in Tiny Umbrella. This is my understanding from what you replied to me with.

If you don't have any blobs saved for 4.3.3, then there is nothing you can do. There is nothing anybody can do, trust me. I proved this to myself last week. I knew what would happen before I attempted it too. But, proof is in the pudding

Good luck

ahhhhh
as soon as i tried restoring, my phone got stuck with itunes logo, with error 20 on "itunes screen on pc"

tried running fixrecovery, same logo persists !
stuck again

Hi

Error 20 is dFU problem; your blobs are definitely saved so you should be able to downgrade okay.

Follow my list again, delete the hosts file again before you start.

Start Tiny Umbrella, start TSS server, goto advanced tab and uncheck 'save settings on exit' or something (not at home).

Now put iPhone into DFU mode by doing this (shokka9's way):

1. whilst phone is on, hold sleep button (top) and home button in, count to 10 then release the sleep button (top), continue to hold home button for about 6 seconds.

2. Tiny Umbrella should recognize it in DFU mode too.

3. Open iTunes and start following my guide.

Good luck bro

Thanks for the good support bro...
Few doubts b4 I start- should I delete the host file before starting tinyumbrella?
Doubt arose only cos tinyumbrella gave a warning popup while starting and ur previous 'instructions' doesn't say anything too
I had serious trouble in putting phone on dfu mode with tinyumbrella opened. Everytime my iPhone restarted as soon as I released power button and returned to iTunes logo on screen. So I had to try restore wit iOS 4.3.5 working iPhone which gave error 20 within seconds of starting restore

I might try downgrading again tOmorrow
Will it seriously affect my iPhone hardware, it's just 4 months old.
Can u pm me ur yahoo or gmail I'd so tat I can be in touch with you wen I do it tomorrow at this time.don't mind !

Actually I am not aware how I got 4.3.3 blObs saved, coz I haven't used tinyumbrella wen I was using 4.3.3 neither I was aware of so called blobs before hope it's a working one !

Dfu is easy wen I start tomorrow with iOS 4.3.5 running iPhone.

Once a failed attempt has occured,itunes stays on screen and it's really hard to turn off pressing the power button.as soon as i release power button and continue pressing HOME button, either itunes or tinyumbrella recognises my iphone and ophone restarts with the same old itunes logo its very annying as the so called BLACK SCREEN IN DFU mode never appears!!

Error 20 occurs during the initial phases when iTunes prepares to load restore on iPhone, I think u must be right, it should be dfu problem.... Shall let u know more about this tomorrow
Thanks for bein in constant touch bro