You can use a custom build of PwnageTool to create a jailbroken 4.0.2 firmware to restore to. You have to be previously jailbroken using Pwnage, though. I just jailbroke my old 3GS last night on 4.0.2
Would this work since in iTunes I backed up my iPhone 4 running 4.0.1 if I restored the phone with that back up and just delete the content I don't want would that work?
Would this work since in iTunes I backed up my iPhone 4 running 4.0.1 if I restored the phone with that back up and just delete the content I don't want would that work?
My iPhone 3GS wouldn't restore using the iPhone 4 backup... iTunes gave me the option of restoring an old 3GS backup from June. Has your 3GS been previously pwn'd, and do you have the old bootrom?
No, restore backups on itunes have nothing to do with SHSH's.
You will not be able to restore your phone to anything but the latest firmware version unless you have your shsh blobs saved locally or thru cydia.
The backups on itunes is just your contacts, texts and other info thats put back on the phone after its restored. Nothing to do with downgrading.