Good Riddles

Question: Four men walk into the desert. Suddenly all four are simultaneously knocked out. They awake buried to their heads in the sand unable to look anywhere but straight ahead. They are positioned so that each man sees another's head before him. However between the first and second man there is a separating wall. So the first man sees only desert. The second man sees only wall. The third man sees another's head and a wall. The fourth man sees two heads and a wall. On top of each mans head is a hat. The underside of each cap is black, but the outside of each cap is either blue or white. Before any of the men can speak, their captors tell them if they speak, they die. However, if any of them can guess the color of their cap on the first try they go free. The captors tell them that there are two blue caps and two white caps. Being an omniscient observer of the situation, we know that the order of the caps are: blue, white, blue, white. So knowing the perspective of each man in the sand, and that they can only see the color of caps/wall/desert in front of them, which of the four men knows for certain the color of his own cap. More importantly: why?

Question: I guide you but you can't hear me. Without me you would be lost. I keep going and won't be stopped. What am I?

Question: Mom and Dad had four girls. Each girl had one brother. How many people are in the family?

Question: A criminal is brought into a prison for major crimes. The warden informs him that he will be shot in the middle of the prison by 20 of his men. The prisoner is fine with that but he asks for some conditions "All of your men must stand 20 feet away from me and I must be able to select where each of them stands. If I survive, I get to leave."

The warden thinks about it and knows that all of his men will still have an open shot at the criminal, so he agrees.

The next day immediately after the firing squad is positioned the criminal walks out untouched. How did he do it?

Question: You struggle to regain me.
When I'm lost, you struggle to obtain me.
I pass no matter your will,
but I'm your slave to kill.
What am I?