IPhone 4s to the iPhone 5 upgrade while on a plan?

I've herd that if you have a iPhone 4s still on a plan (which i do) you can upgrade it to a 5. Like hand it in pay a bit extra and receive a 5 and just pay of that? Is this true? How does it work and how much? I would love to upgrade to the 5 but my 4s is on a plan still and i'm still paying it of, can i still upgrade?

ITunes - Unable to load data from sync services?

The majority of the time when I plug my iPhone into iTunes this message pops up and it doesn't allow me to sync my library. On the odd occasion this message doesn't show up but I'm tired of always having to wait for that odd time to put new music on my phone.

If anyone knows how to fix this it would be greatly appreciated.

Can I buy an iPhone from Best Buy/WalMart as an upgrade on my plan?

I want a iPhone 5, but Sprint is out of stock and I don't want to wait 3 weeks for the shipment. If I go to Best Buy or WalMart and buy the iPhone 5 there, will they acknowledge my plan and sell me the iPhone at the price of an upgrade? If yes, do I then have to take it to Sprint to get it all situated or is everything fine from there?

My iphone messages app froze

I spammed my friend to thepoint my messages app froze. I turned it off and on and it still doesn't work. Its been about 10 minutes now what do i do?

My iphone 4s will not restore on itunes?

I recently decided that i wanted to delete everything off of my iphone 4s to get a fresh start, so i went on itunes to restore it. Everything was going smoothly until the last second where it stated that i couldnt restore my iphone because there was an error. Any suggestions?

Iphone 5 vs iphone 4s screen size?

I know that the iphone 5 has a 4" diagonal screen and is larger than the iphone 4's 3.5" screen (finally) but I can't find the width of the screen sizes to compare. What is the length and width of the screen sizes between the two? Everything i'm able to find just lists the diagonal screen sizes.

Will my music stay on my iphone?

I just got my iphone and i need to update my itunes and i don't have time to now. I used home sharing to get my music on my iphone, but when i leave my house and i'm no longer on the same Wi-Fi as my laptop, will it still be on my iphone?

Added (1). And if it does stay on my phone will it run up my internet usage?

Added (2). And if it does stay on my phone will it run up my internet usage?