Difference between Project Diva and Project Diva Extend

Difference between Project Diva and Project Diva Extend?

If you don't know what I'm talking about I'm talking about the Miku Hatsune games made by Sega.I want to know the difference between these two games.Does Project Diva Extend have more songs including the ones in Project Diva? Or what?? Oh and another question in play-asia.com they have Project Diva "Ohaidoku-han" is it the same as Project Diva.One last question they also have Project Diva 2nd and it says "Low Price Edition" is is the same as the Project Diva 2nd at original price?? Thank you!!!:)