Question

I want to develop facebook applications and I have bought some books from amazon. But this books contents are for old facebook APIs. (2008-2009).
Can I develop applications with old api? Or I have to use new version?

Answer 1

You can still use the old api’s, but as you can probably imagine it is discouraged. Read more in the facebook developer documentation.

EDIT
Given your name, I assume that you know a bit of php. To get started just go to http://www.facebook.com/developers and create a new application. Facebook then presents you with the following tutorial, that I think you should be able to follow:

Step 1: Download Facebook’s PHP Library

Extract this archive into a directory on your hosting server where you can host and run PHP code:

$ curl -L http://github.com/facebook/php-sdk/tarball/master | tar xvz
$ mv facebook-php-sdk-* facebook-php-sdk
$ cp facebook-php-sdk/examples/example.php index.php

Step 2: Replace the IDs in index.php to have your own app information

It should look like this when you’re done:

<?php
// Awesome Facebook Application
// 
// Name: YourAppName
// 

require_once 'facebook-php-sdk/src/facebook.php';

// Create our Application instance.
$facebook = new Facebook(array(
  'appId'  => 'CHANGE_TO_YOUR_OWN_APP_ID',
  'secret' => 'CHANGE_TO_YOUR_OWN_SECRET',
  'cookie' => true,
));