Identify the hidden meaning behind this picture?

There once were seven dwarfs who were all brothers. They were all born two years apart. The youngest dwarf is seven years old. How old is his oldest brother?

What has many teeth, but cannot bite?

How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

Three doctors said that Bill was their brother. Bill says he has no brothers. How many brothers does Bill actually have?

The answer I give is yes, but what I mean is no. What was the question?

The centre of the third figure is empty. What digit should fit inside?

You have four chains. Each chain has three links in it. Although it is difficult to cut the links, you wish to make a single loop with all 12 links. What is the fewest number of cuts you must make to accomplish this task?

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the bridge?