No you cant download it free, Read Here
Yes that’s correct , as now current version is available is paid version CS6. Adobe download page for Photoshop CS2 is available with serial no.
Currently they did not announce officially , but yea they are giving away old version free so in future you will buy latest version.
As I am writing this blog post link is live and may be pulled down later so link is working.
Sr. No is also given on the page.