Iphone 4 won't restore through itunes? Comes up with error 306?

My iphone won't turn on, or reset using the home and the power button it just stays on a blank screen. So I've been trying to restore it through recovery mode in itunes on my laptop. However when it comes up with the iphone recovery mode and gives the option to 'restore iphone' I click on it and it comes up with 'The software update server could not be connected unknown error 306'.
Anyone any idea how to fix this?

Do I need a new iPhone 5 battery?

How do I know if the jailbreak is messing up my battery or if I need a replaced battery? I can go to bed with my phone in the 90% wake up and it will be on 1% sometimes! Then when it's on 80% or in the 70% range it will go off and say its dead but once I plug it back up, it comes back on to 70% range or the 80% range. I'm seriously about to break my phone! It's a iPhone 5 also if that helps!

Updated: Today it went of on 93% and said it was dead. I plugged it up and it came back on and said it was 88%.

How to get my itunes on my new computer?

For years I've had my itunes on my moms computer. Several months ago I bought my own computer. I haven't moved my itunes yet. My mom was having computer problems and had the computer completely cleared. So I'm pretty sure my itunes is gone from that computer. I have all my apps, songs, contacts, pictures, etc. On my iphone right now. How can I get what's on my iphone onto my itunes on my new computer?

Transferring sim to iphone 4?

My friend has a contract with T-Mobile and her handset is roughly 3,000 years old. I want to give her my old iPhone 4 but I'm not sure if we can transfer her contract/number to my old iPhone? Is this possible, and if so, how do we go about it? I was with Vodafone, not sure if that info is needed.