Does the road wind up-hill all the way? Yes, to the very end. (1-2)
Right off the bat, Speaker #2 is giving us just as much information as is necessary to answer the question. This leaves lots of things unanswered, such as "Where does the road go?" "Exactly how long is it?" "How does Speaker #2 know about this road in the first place?"
Will the day's journey take the whole-long day? (3)
Generally speaking, if something is described as a "day's journey," you would likely assume that it would take a significant portion of "the whole-long day," but not Speaker #1. His excessive questioning is another way in which doubt factors into the poem because, as the questions indicate, he's starting to doubt his ability to make the journey.
May not the darkness hide it from my face? You cannot miss that inn. (7-8)
Both questions and answers are short and simple. This makes the questioning seem more incessant (increasing our perception of Speaker #1's doubts) and the answers more vague (since short answers can only resolve so much).