If you ever need to find an i Phone baseband version number, these instructions show you how to do that.
Apple allows you to restore to the latest i OS versions only to prevent users from downgrading to an older i OS version, which would have made it easier to jailbreak the i OS device.
Tools like Tiny Umbrella have allowed you to save the SHSH blobs, so you can use it to create (stitch) a pre-signed IPSW file, which could then be used to restore your device with an i OS version that Apple was no longer signing.
The instructions below will guide you step-by-step on updating your i Phone 4 to i OS 4.3.3 in such a way that you can PRESERVE your baseband for an unlock in the future.
So you cannot restore to 6.x using SHSH blobs except on i Phone 4, i Phone 3GS, and i Pod touch 4G (and i Pad 2 to i OS 5.x if you have i OS 4.x and i OS 5.x SHS blobs).
Despite the lack of support for new i OS versions, it is considered a good practice to take a backup of the SHSH blobs, so if someone discovers a way to hack the restore process in the future to again using the custom IPSW firmware file, then the SHSH blobs would come in handy.
Those wishing to update to this new firmware can do so via i Tunes easily by simply connecting their i Phones to i Tunes, and hitting UPDATE.
However, if you wish to unlock your i Phone later, you will run into problems later if you update this way.
Now that you have updated to i OS 4.3.3, you can easily get an UNTETHERED JAILBREAK RUNNING i OS 4.3.3! Your Word Press website will never be that slow-loading junk that you get with shared hosts!