[Jayz2K]

When I hit "right", i land on the list zone and the home menu is hidden and replaced by the "A column", letting see the info panel and the movie fanart and the status bar on the left, which contains an important info for me : the number of movies in the playlist

In your viewtype, set "Sidebar Autohide" to HIDDEN, then the sidebar won't overprint when you press right.

My question is : is it possible to have this information (number of movies in the playlist) in the view when i'm still on the home menu. For instance, add it in the header of the bloc 4 (at the moment it displays the name of the item menu and the name of the widget playlist, ex : Films / Films unseen recently added)

ATM, not possible. The only bloc that contains this info is Bloc2.

And I have a bonus question, even if I ended doing differently.
At the beginning I wanted to have the bloc 4 (home art) displayed by default, and the bloc 3 (movie art) displayed over it, same zone, but only when i go on a movie from the widget list.
I don't think it's possible?

Right, not possible. I add to define layers depth for consistency is Bloc4 is defined over Bloc3 (when video is playing for example).