6. Are there any works that I can use freely without having to obtain permission in respect of copyright?
Yes, works that are said to be in the "public domain" may be used freely. These works include works which are out of copyright (i.e. the copyright period has expired), or which fail to meet the requirements for copyright protection (e.g. names, titles, or short phrases — they may, however, be protected as trade marks).
Note that the fact that a work is made freely available (e.g. posted on a website) does not imply that the work is in the public domain. It only means that the public are given free access to the work, but they are not given the right to copy the work or commit any act which infringes the copyright of the work.
If a work is not in the public domain, one can only use it without the permission of the copyright owner if one's act is a "permitted act" under the Copyright Ordinance (see "permitted acts" on section II). In cases of doubt, it is recommended that permission of the copyright owner be obtained.