Found a way to downgrade the iPhone
Download the iPhone firmware included in the Restore.zip file.
1. Open System Preferences, click "Sharing", enable "Personal Web Sharing" if it's not already enabled.
2. Copy "version" (included in Restore.zip) and "iPhone1,1_1.0.2_1C28_Restore.ipsw" into:
Your Hard Drive Name/Library/WebServer/Documents
3. open terminal and issue the following commands:
(enter your root password when prompted)
4. You should now be in the nano text editor, to your "hosts" file, add:
5. Press Control-X to exit and save when prompted.
You may need to reboot to make the hosts changes take effect.
6. After reboot itunes.com should be an Apache-Webserver site.
7. Now delete your old firmwares from User/Library/iTunes/iPhone Software Updates/
8. Restore your iPhone with iTunes (iTunes downloads the FW from your created Webserver)
9. Enjoy :D
In some cases could appear errors. I am about to fix it (please help me)