What does this simple rebus mean?

Solve the rebus riddle in the picture below.

They are three errirs in this question. Can you find them?

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

Can you replace the question mark with the correct number?

What number when divided in half becomes zero?

What is next number in the pattern below:

131 517 192 123 ?

_ _ _ IE _ _
_ _ _ IE _
_ _ IE _ _
_ _ IE _
_ _ _ _ IE

Like you see, some letters have gone missing from these words that contain the IE pair at some or the other place. The letters that will be used to fill the blanks are given below. Use them and form meaningful words. Can you do that?

A, C, D, F, H, K, L, M, N, N, O, R, R, S, S, S, T, T, Y and Y.

Name a key which is hardest to turn.

If a zookeeper had 100 pairs of animals in her zoo, and two pairs of babies are born for each one of the original animals, then (sadly) 23 animals don’t survive, how many animals do you have left in total?