Yes. They're all correct and all mean exactly the same things and can be used in any situation when addressing anyone.

I disagree. There is a tremendous amount of overlap between the situations in which the three sentences can be used, but there are differences in nuance. The main difference is that (A) and (B) would most often be used to ask about a single event. (C) could be used for this, but it could also be used to ask about the schedule of the train, especially if the train leaves at the same time every day of the week. Neither (A) nor (B) would be used for this purpose.

A slight difference between (A) and (B) is that (B) is more likely to be said when the train is already present at the time the question is asked. (A) can be said whether or not the train is present; that is, it is slightly more likely than (B) when the train has not yet arrived.