Does iPhone have to be jailbroken to work with T-Mobile service?

My friend is letting me buy his iPhone 4 from him and I have T-Mobile as my phone service. He has At&t, which means it's possible to make it work with T-Mobile since both use sim cards. I was just wondering if the iPhone needs to be jailbroken in order to unlock it in order to work with my T-Mobile sim card or is there another form of unlocking to make it work.
I wouldn't really want it to be jailbroken because I remember jailbreaking my iPod Touch a while ago and it completely messed it up eventually.

Also, where can I take it to unlock it? Do I have to do it myself or can I take it to a T-Mobile store? I don't know if it's against some rule to do this.

How to download emailed e-books?

My friend emailed me links to 3 e-books that I have to download somehow. I would like to either read them on my Mac or on my iPhone but I'm not sure how to put them there. If I download them from the email, they show up in a locked document. Any help would be appreciated!

IPhone 5 used 1GB of Data in 4 days?

I just got a new iPhone 5 with verizon, and had to switch from my unlimited plan to 2GB data a month. I thought this would be fine since I checked my passed couple months of usage and I never totalled more than about 3GB a month. But with my new iPhone, verizon says I used 1 GB in just 4 days. How is this possible? I've tried getting apps that track data usage, but they don't tell me what apps are sucking up all my data.
I'm using data at a normal level, checking facebook, looking up bus directions, and other small things like that a few times a day. Does this really add up to 500MB a day? Is there any app out there that reports exactly what your data is being used on? Are there certain background things I should turn off? Thanks

Added (1). I had data turned off all day, and I turned it on for literally a second, and in that amount of time 339MB were used. There has to be something wrong since I had no other apps open

How to transfer music from iPhone to iTunes without the music being deleted

Ok so my macbook recently had to get a new hard drive (i think thats the name of it) and all its data is erased. Now when i try to get on iTunes to download the music from my phone, it says if i sync the music only the music from the iTunes library will be on my phone and all of my phone music will be deleted. I think there's a way to do it with a disk but i'm not sure how to get music from my iPhone on to a disk either.

any help and suggestions on how not to get my music deleted but to be able to sync my music to my macbook?

How to put an iPhone from the apple store on my verizon plan?

I have a verizon droid. The contract is up and I'm eligible for an upgrade. If I buy the iPhone 5 from an apple store am I still able to get the discounted price? Second if I'm, am I able to put it onto my plan? 3rd if this is not possible does anyone know how long the verizon preorders are going to be? When will they be available for pick up?

Added (1). This is very important my phone broke and I need a new one for work.

Can I open word and pdf files on and download files to iPhone?

I have been using Nokia phones and Symbian OS for a very long period and considering buying an iPhone for the first time.

I was wondering if:

1) it is possible to view & edit word (or even excel and powerpoint) files on iphone?

2) it is possible to view pdf files on iphone?

Please comment if I need to install an application for viewing these files. Recommendations of applications is greatly appreciated.

3) Assume that I sign on my email account and want to download the attachment file of an email to the internal memory of the iPhone. Is that possible? If so, does the iPhone let me where (specific folder for instance) to download the file? For instance Symbian OS pretty much works as Windows where there are already-established folders within the internal hard drive of the phone and I can create a folder if I want and name it how I like it. (I do not require the same from iPhone.

4) Is there a search function on iPhone? Is that really good? For instance on Symbian OS I can search a word/phrase and the results yielded are sorted according to the applications. For example, if that word is used under the phonebook, a couple of text messages and a word file within the internal drive of the phone, then 3 categories show up, and for example I click on "Messages" to see the text messages.

ITunes won't let me transfer apps?

I currently have a jailbroken iphone 4 on iOS 5.1.1 and it won't allow me to transfer apps from my phone. When I click sync on iTunes, instead of allowing me to click Transfer Purchases, it just says 'are you sure you want to remove these apps from your phone'. This did not happen before. I have installous 5 and appsync for iOS 5.0+. I tried reinstalling appsync but it still didn't work.

Can anyone tell me how to fix this?

How to unlock iPhone 3 without a computer?

My connection is too slow (20kb/sec) to download iTunes onto my computer. I already have an iTunes account, I just don't have a computer to do the initial unlock of the iPhone with. It's stuck on a screen that shows a picture of a usb with an arrow towards the iTunes symbol. How do I unlock it without downloading iTunes?

IPhone 4S Cell-phone plans on Sprint?

How much does Unlimited Data, Text, and 300 calling minutes cost monthly? I couldn't find the price on Sprint's website. If you do find information, please give me the link of where you found this info.