Yes, it can. That logo has artistic and design elements, thus is legally regarded as a work of artistic creation, and therefore is protected by the copyright law.
No. You'll only have copyright problems if you use footage or music from the films, and half the time they seem to let that slide anyway. However, although names are not copyrighted, they are part of a trademark and therefore protected by Trademark or Service rights. You may want to look into that.
Frederick Warne & Co. own all copyright.
Mattel Inc has not and never had copyrighted Harry Potter.
2003.
1998.
Harry Potter will appear in the Harry Potter books. If he was to appear in any other published novel it would violate copyright.
No, you would be violating copyright.
2007
I did, did you?
On youtube.
Youtube
Yes. just try searching 'harry potter and the deathly hallows trailer' into YouTube and it should be the top one. I havent been able to see them yet but look forward to. hope this helps!