How to delete everything on the iPhone?

I just got my mom's old iPhone 3, and it has a LOT of useless apps and her old phone numbers and email and all that. How do I make it so that it's like new again, where it has all the general stuff on it like wheather and settings and iTunes and all that? So I can start from scratch?

Iphone 4 IOS 6 Mobile Substrate not functioning

I just Jail broke my Iphone 4 after 2-3 weeks of use and It was working fine and dan.until I accidentally shut it off. This happens to be a tethered (or semi, whatever they call it) Jail break. When I just booted it on the computer it was fine. Until I tried to use any of the Cydia apps. I opened up activator (one of the featured apps) and it said something about mobile substrate not working, and that the device was on safe mode. I couldnt deactivate Safe mode and none of the Cydia apps work. Please help! I have tried Just booting it and even reinstalling the jail break but none works. What do i do!

IPhone 4 Screen replacements?

I have been looking for places to buy a screen replacement for my iPhone 4 GSM (ebay, amazon, craigslist, etc… ) but i'm not comfortable with purchasing them because last time i bought one off the internet, it had some defects and i know that these are not original apple screens, and even if they are, maybe refurbished, etc… Does anyone know where i may be able to find authentic/genuine iPhone 4 screens that do not have any defects?

Jailbreaking a deactivated iPhone?

I have an old iPhone 3 and my contract with Verizon has expired. So basically I can't call or text anyone anymore. I recently updated to iOS 6 and have been considering jailbreaking my device. This will be my first time jailbreaking an iDevice and I was wondering if I would still be able to renew my contract after doing so.

Dropped iPhone 4 in Pot of Water but its working fine?

I'm really nervous about this I dropped it in a huge pot of water and I'm afraid I messed it up, and if I did I won't be getting a new one and iPhone 4 is some expensive ***, Excuse my language but anyway it is working perfectly fine but I'm still nervous about it being messed up now somehow. Do you think it's fine or should I do something like put it in white rice or something?

Can I buy a used iPhone 4s and use it with my AT&T plan?

I currently have a simple non-smartphone (is that even a word?) If I was to buy a used iPhone 4s could I take it into AT&T and have them put a sim card in it for me and use my current plan? How could I switch to an iPhone without an upgrade?