Ok well as the title says it all let me show what I have been playing with.
First up the tools and the platform I used.
Windows 7 Ultimate 64bit
Snw0breeze v2.6.1 for 4.3.2
Sn0wbreeze v2.1 for 4.1
Tiny Umbrella v5.00.11
Fixrecovery for Windows
iPhone 4 32GB -> only blobs are 4.2.1, 4.3.3, 4.3.5, 4.3b1, and all iOS 5 betas.
So you might be asking yourself "why the hell would I want to downgrade?" well I don't really know myself, I was just playing with a theory I had and decided to test it out and here are my results, with lots of pretty pictures.... lol
Ok so lets check out the phone and the blobs saved in Tiny Umbrella, be assured I have checked to see if there were any other blobs saved on cydia and there were none.
So as we can see I don't have any blobs for 4.1 or 4.3.2
At this point I like to open USB View just so I can be sure of the phone's status before I do anything
What you do next is make a custom firmware with the appropriate sn0wbreeze, I'm not going to go through that as there are many tuts on that just search and you will find them.
You can at this point if you want use the DFU helper at the end of sn0wbreeze to put your phone into pwned DFU mode.
If you don't want to use sn0wbreeze then you will need to use redsn0w to achieve the same thing, the only difference is it doesn't matter what firmware you select to put it into pwned DFU mode.
Right so once you have the phone prepped and your custom firmware ready you need to open Tiny Umbrella and run the TSS server, you need to do this as if you don't then itunes will spit an error out at you and you won't be able to load the custom firmware on.
Remember to check in USB View that the phone does say DFU mode.
Ok the big part, open iTunes and it will detect the phone in recovery mode.... lol we know it's not because of USB View, guess that is Apple just dumbing it down for the masses.
Click the ok
NOW VERY IMPORTANT, you will need to hold the shift key down when you click restore, this will give you the option to select your custom firmware.
Go ahead and select your custom firmware.
iTunes will give you a message about contacting servers to verify the restore, pfft don't worry cause you got Tiny Umbrella going..... don't you?
Ok at this point you are now a passenger, let iTunes do it's thing and if all goes well you should recieve a message at the end telling you that your phone has been restored and will restart.
Well guess what? The phone will restart alright, but in a permenant DFU loop. You can confirm this with USB View.
This is what got me stumped at first and took me a little while to find a solution.
So what you need to do now is close iTunes and start redsn0w.
Pretty much follow the on screen instructions at the start until you get to the options screen.
From here select "Just boot tethered"
Now have a little patience here as it seems to take a little longer than usual. You should at first see the Apple logo with the progress bar then it should change to the famous pineapple logo.
Then hey presto it should boot up.
Now depending on what you selected in sn0wbreeze (activated or not) will depend on what screen you are greeted with, i.e. the activation screen or the battery charging screen.
Although this method works (I have now successfully done it over 8 times) it is a permanent tethered downgrade. So far I have not been able to figure out how to make it untethered.
So if you are not sure what tethered is, it means it WILL go into DFU mode loop if either you turn the phone off or it runs out of battery. I didn't test respring though so not sure on that.
Ok so you may still be wondering why the hell would you downgrade, well my theory was that if you could get a custom firmware on there that you didn't have SHSH blobs for you might be able to downgrade and
use iFaith to then get the blobs of a firmware you didn't have or wanted.
So I guess you want to know if that worked right?
Well have a look at the pics below first then I'll tell you.
So sadly I think the pics really say it all. iFaith will run, the phone will start dumping, but everytime I tried there is a "sequence of bytes" missing. I can only
assume that either the custom firmware omits that part, or the tethered boot is the problem. Either way that's where I got stuck and just have not made any progress.
Anyway I thought it might be worth sharing with you all as you never know, someone else might have the tools or the know how to finish this....
N.B. The firmwares I have tried are
4.0.2 unsuccessful to boot
4.1 tethered boot ok
4.3 tethered boot ok
4.3.2 tethered boot ok