The iphone 4 doesnt have problems with mms i have a iphone 4 and it's perfect....did u have the CYDIA app on the phone if so it was jailbroken and if you had the tmobile sim card it was unlocked but i dont know what kind of unlock, jailbreak and unlock are two different things....you can see if your phone is factory unlocked by going to this website ---> iphoneimei.info
If it says not unlocked then your iphone was unlocked through cydia and there for you cant update your phone to the latest ios software because you can lose your unlock