Ok so I bought an iPhone 2g not so long ago and it came with official os 3.0 from apple. But I noticed that it made my iPhone have a shorter battery life. I tried to downgrade to 2.2.1 with iTunes 8.2 (apple tells you to update itunes, or you cannot sync items into your iPhone). I tried going on DFU and it always gave me error 1600... That was so frustrating, and also tried to google a tutorial and did not find even one helping tutorial. I found a solution not so long ago... So follow these instructions on how to downgrade to 2.2.1, how to jailbreak and also unlock.
You need to download the iPhone 2G 5h11a restore from here
9 iPod and iPhone Firmware Download )
Then you need to download quickpwn 2.2.5 for windows from here ( http://miphone.ca/iphone-dev/QuickPwn225-2.zip )
Then you need to download iTunes 7.7 from here ( Download iTunes, iTunes 7.7 Download )
You also need to download and extract Bootloaders from here ( FileSend - BOOTLOADERS FOR iPhone 2G [iPhoneArena@youtube].zip )
1.So now go to control panel > Add or remove programs > remove itunes.
2.Now also go to My documents > My music > iTunes> and erase the iTunes library.itl file.
3.Go and install iTunes 7.7, this is required, you cannot downgrade with itunes 8.2
4.Connect your iPhone, a pop up should come out saying something like "iTunes needs to be updated to 8.2 or iPhone cannot be used" (Something like that...), ignore that, take your iPhone, make sure it is connected and turned on, and put it into DFU mode by pressing both power and home button for 10 seconds, then let go of the power button but keep holding the home button for about 8-12 seconds, until you hear the USB sound from your computer or some pop ups will come out saying your iPhone is connected.
5.After a few seconds iTunes will say "iPhone detected in recovery mode and needs to be restored", press ok and then it will show you a new page, press shift+right click on the 'Restore' button, and look up the iPhone 5h11a restore.ispw file and press ok.
6.Wait for the iPhone to be restored, this time it shouldn't give you any errors.
7.After it is done, you have 2.2.1
Jailbreaking and unlocking
Turn on quickpwn, look up the ispw file, and continue, follow the instructions, and if you want to unlock, it will tell you to browse and upload the bootloaders 39 and 46.
Have fun... Please give me credit...