No. Not all creative works are protected by copyright. There are many exceptions to and limits on copyright protection. For example, copyright only protects creative works for limited periods of time. After the period of protection expires, the copyrighted work enters the public domain. If a work is in the public domain, the work may be freely used without permission from the creator of the work. However, just because a work is available online does not mean it's in the public domain or free to use.
The copyright laws of many countries have specific exceptions and limitations to copyright protection. For example, in the United States, "fair use" allows you to use a copyrighted work without permission in certain circumstances (e.g., a book review that includes some of the book being reviewed).
It depends; sometimes it is fine to upload copyrighted materials to Microsoft's websites without seeking permission from the copyright owner (e.g., backing up your personal files, such as your family photos, on OneDrive). However, we are generally required by law to disable access to copyrighted content (including videos, music, photographs, or other content you upload onto a Microsoft website) if the copyright holder claims that the use of the copyrighted work is infringing. You can let us know if you believe that a copyright holder wrongly requested that we disable access to content you uploaded (e.g., you believe you have the rights to use that content or because your use is a fair use). Note that if you repeatedly use your Microsoft account to infringe, we may terminate your account. So please, respect other people's copyrights.
If you believe that content hosted by Microsoft infringes your copyright, contact us by visiting Notices of Infringement and complete the information requested there.
Some content available online, such as public domain content, is free to use because it is not subject to copyright protection. Other content might be subject to copyright, but the copyright holder licenses content with certain restrictions, such as under the Creative Commons license. Bing's image search lets you limit results only to Creative Commons-licensed images (after running an image search, click "license"). Other copyrighted content may be used without permission because a limitation or exception to copyright applies (see above discussion of fair use).
It depends, but it is generally a good practice to credit the original creator of the content. Some content creators require that you give them credit when you use their work as a condition of use. You should carefully review any license requirements for any content you plan to use prior to using any content.
For more information regarding Microsoft's web crawling and site indexing practices, refer to the Bing blog on the Robots Exclusion Protocol.