There seems to be some confusion here.
1. The MSL will not unlock your iPhone. It is used for updating the carrier information. AGAIN it will not unlock your phone. If spring gave it to you it will only update sprint information that is it.
2. All iphones are un-trademarked. The phones are programmed for the select carrier.
3. The lock resides in the Modem revision. So restoring your phone will not do anything other then restoring it.
4. You can not unlock a sprint phone. The only way to do it is with a GPP sim card from ebay. And that work 20% of the time with no internet most of the time. Also no MMS. To get these to work you better be an IT person. There are all trial and error. (Not a method i really suggest.)
5. The only carrier you can use this phone on are PagePlus and Freddompop. Unless the phone has a bad esn. And in that case only PagePlus. This also goes for verizon iphones 4s.
I hope this answered all the confusion. There should really be no other questions.
Here is the best option. Sale it and buy a GSM version.