How to unjailbreak my iPhone 4 CDMA tethered?

Hi, I tether jailbroke my iOS 6.1.3 CDMA iPhone 4 and want to unjailbreak it. Every time I go to restore it, my computer says something about the phone not being eligible for the requested build. I'm currently trying to do the "Erase all content and settings" then, when it's done, I'm gonna try to restore it again. Does anyone else know how to solve this issue? Answers are greatly appreciated. Thank you.

Added (1). Basically I tried to restore it and that's what came up…

IPhone 5, iTunes and Mac software?

Ok I just got my iPhone 5 today and I'd like to transfer all the music from my iPod to the iPhone… But my dad hasn't updated our mac for a long time, and I need a certain iTunes to make iTunes recognize my phone, but for that I need to update a new mac os x and I can't find the one that I need anywhere! Is there some way anybody can help or new solutions so i can get all my music from my old iPod to my iPhone?

Sony vegas 12 won't open. MP4?

I have lately upgraded to windows 7 ultimate (64 bit), and while i was at it, i decided to upgrade to Sony vegas 12.
I run a youtube video, and i record with my iPhone 4s, iPhone 4s records in. MP4 and now Sony vegas 12 refuses to open the video file! -.- Yes, i do have quicktime installed, Any Suggestions?

My iPhone 3G keeps kicking me off my message app, why is this happening?

My phone has been kicking me out of my main iPhone messaging app. And I don't know why. Before this happened my friend had been texting me long emoji texts then I go to open one up and it just kicked me off and took me to the home screen. I've tried turning it off. Restarting. And updating my phone. But nothing worked. How can I fix this because I can't open up the app to reply to really important texts.

How to remove the marvel chara-cover from the iPhone?

I just recently bought the iron man chara-cover and its supposed to slide on and off by the head of iron man. But now it won't come off and apparently that's an issue with these. I've pulled like crazy and it won't budge at all. Does anyone have any suggestions without breaking or damaging the case?