You can downgrade only if you have 4.xx blobs saved previously to get untethered jailbreak. Were you using Gevey sim before the restore ?
You cannot do anything to the updated baseband. Switch to official carrier , use it as itouch or sell it and get a factory unlocked iphone or wait for a new unlock.
Nah this is the first iPhone i ever tried to JB so im not sure what Gevey sim is and i also dont have any 4.x.x blobs is it possible to get them from somewhere? like another iPhone perhaps