That last guide is wrong you have to pay to get into the Queen Mary because it is a tourist attraction alongside being a hotel there is a general admission to get into the doors I believe it is either $10 or $12 but the good news is that you can use your general admission ticket to get a discount of $10 on a meal at one of the many restaurants
Generally, as with most hotels, yes. But, like most hotels, it is possible to walk around the property without being a guest. Just don't be jerk.
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