I will try to answer some of these for you. I don't speak any Chinese languages, but I do know some things about them.
1. Yes, they speak in different dialects. If you watch a Taiwanese drama and then a mainland drama, you can hear the very obvious differences. Taiwanese also uses a lot of Native words and sounds in the language. Though both are similar, you can really tell the differences and they sound like two completely different languages.
2. In China, Mandarin is the official language so most people speak it. They are taught from a very early age, even if Mandarin dialect isn't their first language. China implemented this because there are so many different dialects/languages there.
3. Cantonese is spoken in the southern region of China. That includes Hong Kong and Guangdong. Guangdong used to be called 'Canton'. Mandarin is spoken in the mainland, mainly in the north and south west, though because it is the official Chinese language, it is taught throughout China and most people speak it. There are many other dialects spoken in China. Those are not the only two, just the two that are most spoken. They are categorized as seperate dialects, but they might as well be completely different languages, because they sound so vastly different.
4. Having English names dates back to Shanghai and Hong Hong pre WWII. Hong Kong was a British colony, so English was an official language there. Many Hong Kong Chinese adopted English names, though most were actually named traditional Chinese names. Before the Japanese occupation of China, Shanghai was a major international city, with different national districts making it up. Along the same premise as mentioned above, many adopted an English name, especially if they worked for a British company or family.
5. Chinese dramas have subtitles so that speakers of other dialects can understand. Dubbing is very popular, too.
6. I tried to learn Chinese and chose traditional as my system. LOL I learned very quickly why simplified was invented. Haha! Simplified system was created during Mao's time and was introduced to make reading and writing easier for everyone. It is still rather complicated, but generally use less strokes to write. In the Mainland, Simplified is the offical writing system. Taiwan still uses Traditional as their official system.
7. The characters in the Japanese alphabet are the same because China invented the written characters. There was a time when most of Asia used the Chinese writing system. It was even used in Korea before Hangul was invented. As for if they have the same meaning, that is something someone else will have to answer, since I don't speak either language. My interest is the phonetics of different languages, so I can answer about sounds and tone but not about meanings and definitions of words. Hope someone can help with that one. :)
