by Luis de Vasconcelos.
Moodle 2.0 and 2.5 are hugely different!
You could try going through all the release notes for each version, example:
http://docs.moodle.org/dev/Moodle_2.6.2_release_notes
http://docs.moodle.org/dev/Moodle_2.5.5_release_notes
http://docs.moodle.org/dev/Moodle_2.4.9_release_notes
http://docs.moodle.org/dev/Moodle_2.3.11_release_notes
etc.
You can find those on http://download.moodle.org/