Jailbreaking and Unlocking with iPhone is fun, but these days apple is trying to make people life harder by introducing new changes in iPhone hardware and software which could stop or prevent people from jailbreaking their devices.
One of the change done by apple is the fix they had done in iPhone 3GS bootroom, they have fixed the potential bug found in old iPhone device which allows to unlock the iPhone to use a different carrier. There is no tool which can unlock an iPhone with new bootroom. Now the question arise here, how could one know whether his / her iPhone has a newer or old bootroom so that he /she gets to know whether their apple devices can be unlocked or not.
How To Check Bootroom Version On iPhone
To check whether your iPhone has a newer or older bootroom, boot up your iPhone and go to Settings >> About
Check your model number – if it begins with "MC" then you have the new bootroom if it is not "MC" then you have an older bootroom also check the 4th and 5th number in you serial number if it is lower then 40 then you have an old bootroom.