Who read The Mousetrap help me please: Now knowing “whodunit,” what were the clues

1. Now knowing “whodunit,” what were the clues that led to the culprit’s discovery? How could you have known the culprit along the way?
2. What were the red herrings that led you away from suspecting the actual culprit? How did they work?
3. How did the detective do his work?
4. How did Agatha Christie do her work in setting up the mystery?
5. Were all the characters two-dimensional (as Edmund Wilson claims) or did some or all have development?