The answer to #3 depends on whether you're referring to casual spoken English or to written English. Your example sentence is much more likely to occur in written English. Spoken English, in particular, casual and everyday spoken English among friends, tends to really simplify things. So you are more likely to get something like: "Wendy, where did you get that watch? It's so strange!" if you really know the person. Or "Wendy, would you mind telling me where you got that watch? It's so strange and interesting!" if you have a less familiar relationship with Wendy. I hope this helps you!

This sentence is perfectly fine and grammatical. This is also the simplest and most natural way of asking the question.