Logic Riddles

Question: How can you flip the shape upside down by moving only two of the sticks?

Question: People see through me, but none pass through without killing me. I can be anywhere, and can be seen double or single. What am I?

Question: If it takes three men two days to dig a hole, how long does it take one man to dig half of a hole?

Question: There are two ropes that both take exactly 1 hour to burn from end to end. You are unable to cut the rope. How can you burn the two ropes in a total of 45 minutes?

Question: Two children are born in the same hospital, on the same year, on the same day, and have the same father and mother. But they are not twins.

How is this possible?