My jailbroken iPhone 4 can't connect to SIM-card after update?

The title says it. I have a jailbroken iPhone 4 and as I plugged it into my computer it asked me if I wanted to update the IOS. The updating-process went smoothly, but when I started the phone afterwards it said that it was unable to connect to my SIM-card (that i bought 2 weeks before this).

Does anyone know how I can unlock my iPhone?

Are iMessages free when using Wi-Fi even with international numbers?

I'm from the USA so I have a US number, but I'm currently in Australia.
I brought my iPhone with me to use with Wi-Fi.

My friend here in Australia has an iPhone (clearly with an Australian number), if I send him a message using iMessage (while I have Wi-Fi), will he be charged because my number is international (& vise versa for if he replies)

ITunes won't open on my computer?

When my iPhone 4S connects to my laptop, my iTunes library opens automatically but now whenever my phone is connected to my laptop, it just says

'The file 'iTunes Library.itl' can't be read because it was created by a newer version of iTunes.'

and doesn't load. This may be because iTunes updated automatically but I'm sure I have downloaded the newest version of iTunes onto my phone and onto my laptop so I don't understand why it's not working.

Has this happened to anyone else and how have they fixed it?

Can Sprint fix my iPhone 4S?

My iPhone just recently started blurring out the Wi-Fi setting and now I can't use Wi-Fi. I checked online using my phones serial number and my one year warranty is still good. I was wondering if I could take my phone back to sprint who I bought it from in the first place and was wondering if they could replace or fix it? If so do I need to bring my mom or something? Because she pays for my bill or can I just do it myself?

Which data plan should I get? ATT iPhone?

I'm going somewhere for 3 weeks and I need to upgrade my data plan because I'll be using Turn by turn directions ALOT! I currently have 300 MB (lowest) of data each month. The next few upgrades are 1 GB, 2 GB, 4 GB, 6 GB, 8 GB, etc. I'll be needing to use the internet more, emails, google, and using maps with Siri. Anyone have any information?