I have try to downgrade iPad 2 to 5.1.1 and 4.3.5 And it is done here's my note guide I hope it can give the idea but I just follow red snow guide if some thing wrong with it don't distract and blame.thanks




I use ipad 2 ios 6 that have been save shsh blob 4.3.5 and 5.1.1.*
mY ipad2 is original unlocking from my country meant no factory unlock.
In order to restore ipad2 version 6 back to ios 5.1.1 (i have test it four times) it ok*
note that i have test it to restore from 6 to 5.1.1 *it can;
we can restore (after downgrade from 6) 5.x and to 5.x again by using only redsnow tool
*not from itune.
we can restore from itune back to version 6 again without baseband update on ipad2 .


**
Tool:
A/tiny umbrella latest version (allow access throught fire wall) to check shsh(4.x,5.x).,ECID(dec,hex),serial number of ipad.
B/Itools or ifunbox to export all apps and important stuff.
C/redsnow 0.9.15b2 or b1 *by click on redsnow exe. run as administrative mode->yes.
D/ firmware save on pc 4.3.5(iPad2_2_4.3.5_8L1_Restore.ipsw), 5.1.1(iPad2,2_5.1.1_9B206_Restore.ipsw),6.0(ipad2, 2_6.0_10A403_Restore.ipsw)for me
* *;-)
***let do it
Activated reds now in admin mode.
Now choose Extra->SHSH(check for valid shsh save in local and remode)->check like
1/new : to connect shsh version 6 by click on it (new icon) choose firmware ios6, ios5, ios4
2/verified: confirm APticket for iso5, 6 (is present) but ios4(APticket missing)
3/submmit:choose shsh you save in pc folder then submit it.
4/query:copy and past ECID and click *ok.
if you see remode blob 4.x,.5.x,....it ok to continued downgrade.

Now choose on redsnow back->Even more->Restore->choose Ipsw version 5.x.x
(we see message to restore to firmware 5.1.1on ipad2, hte IPSW of any ios 4.x firmware for which you have saved blob
also required please click ok to locate 4.xIPSW first....)choose ok->open
choose firmware 4.3.5->open(the device is in recovery mode)->choose blob local(choose shsh all in folderwe save it) or remode->
we see message(please manually enter device DFUmode...)->prepared (not click ok *yet) while your *hand click ipad on lock button and count
3 second then other finger hold home button for 7 to 10second then release lock button while still hold home button 15 to 20 second
*we will see on redsnow (DFUmode )-> click ok(waiting it restore) .finish by just leave it(the restore procedure take two time one
for 4.x another for 5.x.)
Error service non start can fix by just change usb port to another port. done
Error sound ipad fix by go to setting -> general->use slide switch to -> click change from mute to lock Rotation. then back to home screen double click home button
slide all apps from left to right we will see bass icon is mute so -> click it to un mute .done
ERROr fix Ex008...mean usb defect invalid *so we need to remove apple software, itune , replace dock usb if it too old ,scan virus ,update window*
then restart pc ->connect ipad to pc check usb is working by show folder option ,then install itune latest version .that shoud work*
to locate shsh save after fecth to redsnow ,first click folder ->oranized->folder..option ->view->show hidden file extention ->apply it and locate on C:\Users\our pc name\AppData\Roaming\redsnows




Reset ipad2 by erase all content and setting after finis *now goto jailbreak with redsnow just one click on jailbreak.



To res tore agian and again from 5 to 5 do not use itune it will give error 3194
so use redsnow to restore it insteed *by *go to even more to restore choose ipsw 5.x the same version you have downgraded follow it guide .it done.
*



Now in order to restore back to 6 connect your ipad *to pc open itune then it ask for update do not update
click cancel-> click on device ipad -> on the screen *we see *update and restore now click on shift key on pc*
*hold it and at the same time click on restore -> choose ipsw 6 -> open -> restore(ipad now on restore mode
on itune waiting it working (ipad is restore factory setting message just leave it)->set as new ipad-> tick*
the three boxs as which one you want and -> done.
on ipad choose network wifi then enter passcode wifi -> next->enable location-->next(creat or singin or skip the acccount)->next
agree->agree->use icloud->next-> choose our back up-> choose ->(find or don't use find my ipad)->next
(let other find you choose ever you want)->next(diano and usage)->next ->start using ipad.Fins

I'm having a problem, I get error "Service wouldn't start" after the completion of restoring to 4.3.5(I have 4.3.5 SHSH blobs) my iPad 2 wouldn't restore to 5.1.1(the next step)

Only change USB port to be recognition by reds now when you got error all error belong to USB port.so try to do restore again to ios 6 first by iTunes .if still got error check my error note I have post .
TUTORIAL - Failsafe method to restore the current version of IOS

I encounter same problem as JCJeff. Service wouldn't start. It works fine when i just downgrade it back to 4.3.5 though.
And I tried switch to different usb port and wouldn't work.

Ok for me I just change USB port it work .for my idea the way service did not start because of malicious to USB so it cann't connect to red snow during it start or another reason you used to try restore to 4.xto 5.x after downdrading from 6. so in order to make clear our USB work fine try out to remove apple UBS software in control panel on pc and software relate software including iTunes but make sure you copy your iTunes library to your pc beware lost your application ,ok.make your pc upto date by update of PC software and install and scan all virus .Then restart computer ,now plug in iPad then you will see notification on pc about installing apple USB .when it is finish you will see auto run folder it means your iPad USB is pure .now install your iTunes back and run your iPad on iTunes to confirm it reconight without any defect .ok to run red snow now and close your iTunes . For my test it work .thanks
Oh I forgot before doing this restore your iPad to iOS 6 from iTunes first .then manage the USB concern

A "Service won't start" error indicates an issue with the iTunes installation on your PC. It is not aproblem with the iPad. It is indicating that the Apple Mobile Device service is crashing / failing for some reason.

I would recommend a full re-installation of the latest iTunes on your PC. Also, ensure you are using a genuine Apple iPad cable (not a cheap 3rd party one), and you are not connecting via a USB hub, but directly to the PC. Try a differnet port if the problem persists.
Also, it is worth disabling all anti-virus / malware tools whilst you are trying to restore as these can interfere with USB communications.

Ok i gree sir. For my understand of this is great idea .thanks
Here is the video guide from iclarified it is old but almost the same to this thread

[Moderator edit: Removed link to other tutorial. We have one here in the Hacking section, don't need another. Thanks.]

I DONT HAVE A 4.x BLOBS SAVED ANYHWERE, AND I CANT DOWNLOAD IT FROM ANYHWERE!!!!
IM SO CONFUSED THIS IS THE ONLY THING THAT IS HOLDING ME BACK FROM DOWNGRADING BACK TO 5.1.1!!!!
HOW CAN I SURPASS THIS CONFUSION????

You cannot. It is simply not possible. Blobs are highly secure and cannot be faked or bypassed.

Originally Posted by BryT94

I DONT HAVE A 4.x BLOBS SAVED ANYHWERE, AND I CANT DOWNLOAD IT FROM ANYHWERE!!!!
IM SO CONFUSED THIS IS THE ONLY THING THAT IS HOLDING ME BACK FROM DOWNGRADING BACK TO 5.1.1!!!!
HOW CAN I SURPASS THIS CONFUSION????

I'm afraid that you'll have no choice but to wait for an iOS 6 jailbreak release in order to jailbreak your iPad.