what three important questions ran through the novel and were answered at the end?

I suppose one question Winston continually thinks of is "why?" Winston wants to know why the Party does what it does. By the end of the novel O'Brien makes it clear that power is all they want, our and simple. O'Brien clarifies, "If you want a picture of the future, imagine a boot stamping on a human face — forever."

Winston comes to know the "how" question as he learns the dynamics of the inner party. As Winston gets to know O'Brien, he understands the "who" as well.

Also the mystery of room 101 is solved. The most frightening thing in the world breaks the human psyche. For Winston it is rats.

"If you want a picture of the future, imagine a boot stamping on a human face - for ever" this sentece is really frightening!