Products tree, Add to cart [questions]

[Ajvn]

Greetings,
I have few questions about Prestashop.
Why I can't set this in: Back Office >> Preferences >> Products:
Allow ordering out-of-stock product: to NO
It's always return to Yes.

Drop down tree in Back Office>Catalog (etc. near Reset|Filter) for categories and subcategories can be very usefull, and probably improve navigation and faster adding products in catalog. Now it can be very slowly to navigate throughout subcategories (if we have) to add product(s).

How I can import products via .CSV (for RC4)? What is "sorting values" for CVS? I read this:
http://www.prestashop.com/wiki/Importing_Product_Data/
but this is for RC3. Is there any improvements for importing products, like manufacturers, suppliers, Features?

Can I remove from newsletters or other mails "powered by Prestashop" text? I read about open-source licence, but I want to know is this legal to remove?

Regards,
Ivan