Here's my scoop.

* 3Gs 3.2.1
* FACTORY UNLOCKED
* Blackra1n may or may not have been run on it.
* There are no non-iTunes apps on the phone.
* Would like to upgrade via normal iTunes method to latest 4.x IOS.
* Have no need for a jailbroken phone.
* Have no idea about baseband version or any other technical stuff.

If I do this and the phone has NOT been jailbroken, no problem. It obviously updates normally.

If I do this and the phone HAS been previously jailbroken - what will happen?

All I want is a 'normal' functioning phone *with all my current data on it.

I've looked for an answer to this far and wide to no avail. Your assistance is greatly appreciated. Thanks.

Originally Posted by WowIndescribable

Here's my scoop.

* 3Gs 3.2.1
* FACTORY UNLOCKED
* Blackra1n may or may not have been run on it.
* There are no non-iTunes apps on the phone.
* Would like to upgrade via normal iTunes method to latest 4.x IOS.
* Have no need for a jailbroken phone.
* Have no idea about baseband version or any other technical stuff.

If I do this and the phone has NOT been jailbroken, no problem. It obviously updates normally.

If I do this and the phone HAS been previously jailbroken - what will happen?

All I want is a 'normal' functioning phone *with all my current data on it.

I've looked for an answer to this far and wide to no avail. Your assistance is greatly appreciated. Thanks.

Firstly it has to be iOS 3.1.2 - the only device that can run 3.2.1 is the iPad

If it is truly factory unlocked then you should have zero problems in restoring (not updating) to iOS 4.0.2, activating legitimately via iTunes and finally setting the iPhone up as new.

That blackra1n may have been used does not matter. What is more important is that it is truly a factory unlocked phone. These sell for a significant premium over locked iPhones

To avoid a useless brick, you need to check that the phone was not passed off as factory unlocked but instead simply unlocked with blacksn0w. If blacksn0w was used there will be traces in some config files that will indicate this.

You can also check the model number, this gives a rough indication as factory unlocked phones don't end with a /L in the model number. It's still possible to pay off the subsidy/contract on a locked phone and get it officially unlocked - which is why the model number suffix is only a rough indication.

Fabulous information, Olethros, thank you very much. I hope others in my situation find this thread.

You're right about the version, of course. Typo.

The phone was indeed purchased at a premium new from a country that sells genuine factory unlocked phone and from someone with a well-established good reputation. Apple confirmed the unlock when I registered it. It does not have "/L" at the end of the serial number.

That said, perhaps it's worth checking those config files you mentioned. - how does one do this? What should be looked for?

Question: How can (and why would) I "restore" to 4.0.2 when I haven't upgraded to it yet? Or is this just semantics?

UPDATE

After seeking a few more bits of advice elsewhere, I decided to take the plunge. I plugged in the phone and iTunes did the normal backup, then I downloaded and upgraded. It took a long time. The progress bar on the phone looked like it was stuck but every 10 minutes or so it would move about a millimeter. Then iTunes hung - the the progress on the phone continued so I just left it all to keep going. Eventually Safari crashed (?) and then iTunes became unhung and the update finished. All my data is there and I'm on the new IOS4 with everything functioning. I received the Apple message that my phone was unlocked.

My advice to anyone, don't touch anything while the update is running. Go to bed and come back in the morning if you have to.

Originally Posted by WowIndescribable

My advice to anyone, don't touch anything while the update is running. Go to bed and come back in the morning if you have to.

Good advice. Having seen some serious errors occur when people lacked the patience to let the program finish it's job, it's very worth mentioning that once you start a restore, you absolutely should do your best to let it finish itself.