What is the Surname of Barbie Doll?

You stand in front of two doors. A guard stands next to each door. You know the following things: one path leads to paradise, the other leads to death. You cannot distinguish between the two doors. You also know that one of the two guards always tells the truth and the other always lies. You have permission to ask one guard one question to discover which door leads to paradise. What one question would you ask to guarantee you enter the door to paradise?

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

A man dies of old age on his 25 birthday. How is this possible?

What can you see in the middle of March and April that you can never see in any other month?

I’m tall when I’m young, and I’m short when I’m old. What am I?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

You see a boat filled with people, yet there isn’t a single person on board. How is that possible?

In the Thar desert, 3 men found a big 24L Jar is full of water. Since there is a shortage of water so they decided to distribute the water among themselves such that they all have equal amounts of it. But they only have a 13L, a 5L and an 11-litre Jar.

How do they do it?

Which number should replace the question mark?