How to restore an iphone to its default settings? (4s)?

I'm thinking of lending my iphone 4s to a friend while he gets his fixed. But if I do lend it to him I want to give it to him with its default settings (ie no apps, contacts or photos on it).Is there a way I can give it to him without anything on it and when I get it back I can restore everything the way it was before?

What are push notifications? And how to turn them off?

Okay so I'm a 9th grade student and I study in a school where phones are not allowed in school in fact almost every school in my country dosent allow any electronic iteams… But in my school many people bring phones and now even I want to take my phone to the school (I own iphone ) but now the probem is that if I put it on silent mode I'm scared that the notifications in the apps may make that noise and then my phone will get confescated and what I have understood by push notifications is that _ the notifications which come from any app you hav… Is it rit? And is there any way please tell me step by step how can I keep my iphone completely silent so that no one in the school gets to know about it…

Added (1). Thank you so muchhh @june… The best thing I like in your answer was don't fall in peer pressure… U actually made me realised that dosent matter if you don't take the phone yto school… :')

Recover deleted pictures from iPhone 4S?

I lost my phone on holiday and staff in the hotel found it for me in the morning but the somebody pressed the reset button and deleted everything (lost all the holiday pictures from camera roll) so i continued taking pictures with the iPhone afterwards.
Got back home, used my back up to get everything back.once the back was loaded it ended up deleting the new pictures that I took from the holiday and now I'm left with nothing:-(
How do I recover the new picture as they mean more to me and why did that happen?

Where to buy high capacity iphone 4 of battery?

I need to buy a high capacity iphone 4 of battery. I looking for a long time at the ebay and amazon, see a lot of reviews about high capacity iphone 4 of battery. But i don't know which one i should buy? Apreciate any help, thanks.

What site can I use to download books onto my iPhone for free?

I have the app 'iBooks' where I used to store all my books but my phone got wiped and now the site I used to use have taken down the books I'm looking for (Harry potter) the site I used to use is www.epubbud.com and now I can't find a website that is even a little like this.

My iPhone battery drops rapidly?

My iPhone 4 battery drops so fast, even when I'm not on the phone it will drop, I haven't got blue tooth on what should I do?

What happens when you upgrade?

So later this month I'll be able to get an early upgrade with O2. I had an iPhone 4S (it actually got stolen when I was in Paris a month ago and I've filed a police report and got a new sim etc) and I plan on upgrading to the iPhone 5. I've never upgraded before and I was just wondering if there were any catches to upgrading early so I don't really know exactly what happens, do you have to pay extra because it's the newest model? On my 4S I paid £40 a month.

I have 2.5 GB monthly data. I've used 10% within a day.is that bad?

I just bought the iPhone 4 from Cricket on Saturday. I'm allowed 2.5 GB of monthly data. It's now Monday at 12:05am and I have used 10% of my monthly data? I've downloaded 3 apps and have about 25 pictures.

If I go over my monthly limit, my speed will just slow down(that's what a online sales-representative from cricket told me) So uh. I don't want that to happen ha what exactly is causing the data increase? Obviously the apps, but does pictures/text messages increase it as well?