Start by entering the items that belong in the first category. As you guess the answers in the first category, a code for a safe will appear. Type it in to reveal the following safe category. Make it to the end!
It's a principality of the UK because it doesn't not have it's own official governing body. It is under the UK's control and it follows the rules laid down by Parliament in London. Scotland has their own Parliament but it's almost a subdivision because they still need to attend the House of Commons.
http://www.worldatlas.com/articles/15-biggest-cities-in-africa.html