It is generally not recommended to cite a dictionary in a formal paper unless you are specifically discussing the definition of a word. If you must cite a dictionary, follow the specific citation guidelines required by the citation style (e.g., APA, MLA) you are using.
I would just put www.facebook.com
Yes. You should cite the dictionary you copy from.
Yes. Citation in a paper is a matter of academic honesty, not ownership. You would cite references even to other papers that you had written.
Web sites, books, and articles
Scroll down to section 5 in the related link to cite movies.
The difference between an informative paper and a research based paper is that a research based paper must cite the sources of information while an informational paper does not have to cite sources. An informational paper is also written in a simpler format than a research paper.
Anytime you use the work of someone else, you cite it. If you do not, then it is plagiarism.
As you would cite any other piece of information. Who is the creator/author, where was the picture found, when was the picture found. Try to contact the original owner/copyright holder to get permission to use the picture.
a direct quote by someone else
sight Nothing is as beautiful as the sight of a new born baby. cite When you write a reseach paper, cite your sources in a bibliography.
As long as you cite your source, it is not considered plagiarism. But most teachers do not allow you to copy a page, even if you cite it.
It would be a rare occurrence to cite sources that are non peer reviewed within an essay but that does not mean it should never happen. If a wiki puts forward a popular point of view, perhaps a reference to it might be appropriate to show that the point of view exists. To cite a wiki to support arguments set out in the paper would be unlikely to impress an instructor. There are almost always better sources to cite and if there aren't, it is worth considering why no other source has the same view.