Can I upgrade an unlocked iphone 4s T- Mobile to iOS 7?

So i decided I want to upgrade to iOS 7 but the beta version and I want to know if I can do it. My iPhone was originally locked with Sprint but They unlocked it so i can have any carrier I want and I have T-Mobile. They said you need to see the model of the phone such as there's one for sprint & verizon & another one for At&t & T Mobile. The only think i'm concerned about is the model because the phone is originally from sprint.

Yes you can. The unlock never goes away no matter if you update to IOS 7 or not.

Register your UDID at www.udidregistration101.webs.com and they can help you get your proper IOS 7 download links and as well help you get IOS 7 onto your iDevice. They will register you within 10 min.

1st off I wouldn't go to the beta version. I'd just wait for the final, more stable & free to access version.
2ndly when it does come out it will be available for the 4S no matter what configuration

Yes, but you need to register your device's UDID with a developer account through a site like http://www.udid.in/.It's $5, and then you don't need to worry about Apple deactivating your device for running unreleased software.