How to Use MUST HAVE Correctly? Ask Alisha

In this video, Alisha answers 7 questions. - What's the difference between: ""is that how it is?"", ""is that how it works?"", ""that's not what it says"", ""that's not how it works"" ? - Sometimes I see a couple of sentences like :""your dad must have had it for at least 2 years."" Why they do like ""have had""? What's the rules of this? - What is the different between Astronomy and Astrology? - My name is Afeef, I have been studying Pharmacy, and my question is How to make English speaking skill in home alone?? - What is the deference between ""its up to you"" and ""you're up to"" ? - ""What does sunglasses mean?"" and ""What do sunglasses mean?"" ""Sunglasses"" is a plural noun, should we use DO instead of DOES? - What does a spirit animal mean? I don't think we have that kind of question in my country. Also, what are some possible answers?