Here you can hear different ways to pronounce the word "our" (British and American English). http://www.oxfordlearnersdictionaries.com/definition/english/our Probably the two different sounds that you noticed came from different accents. Hope it helps. :)

It depends on accent, and also how much stress you are putting on the word. If the word is important in the sentence, I would say it like 'Hour'. If it's not important, I'd say 'r'.

It could be a class difference in oral accent.  /aʊə/ is standard.  /aə/ is upper class. Search the internet for speeches by British royalty for examples. Note the correct IPA notations: both without a final "r".

Maru, the pronunciation in this case is a result of regional differences. It is the same word, there is no difference in meaning. But different regions, different influences will affect the way that people pronounce certain words at times, especially when the people are far removed from the area of origin. This can be a result of various things, for example, multiple languages spoken in the area. As far as how to truly pronounce it, you will find that some dictionaries only have one way whereas others may list multiple ways as acceptable.