Unjailbreak, unlocked iPhone 4

[cyps86]

I'm in a situation where I need to have my phone back to the way it came from the factory. I would like there to be no traces that i've modified it. Please let me know how I should do that with the following phone...
Device: iPhone 4
Firmware: 4.2.1 (8C148)
Jailbroken: yes and can't remember what software I used
Unlocked: yes with ultrasnow

Any help is much appreciated

[Turnamental]

1. Upgrade to STOCK 4.3.3 ipsw in iTunes if unlock is no longer needed...

2. Downgrade to a fresh 4.0.1 or 4.0 with TinyUmbrella method if unlock will be needed in the future... (keeping the 1.59.00 baseband)

At some point in time that phone had 4.0.1 or 4.0 on it and Cydia should have the SHSH on file...

I would personally take the 2nd route if it's NOT going back to Apple.

See here > [How-To] Using tiny umbrella to update/downgrade/restore

[cyps86]

Thanks for your quick reply and the two options. I will be going with option one as I shouldn't need to unlock it again in the future...
I was under the false impression that if I updated it would brick up... But you're saying it won't (instead no jailbreak and unlock anymore)
Also if I just do option one is there anything else I should do if I don't want to show it had been jailbroken?