Since enotes allows students to ask only one question at a time, I will address your question about puns. (You are welcome to submit your other questions separately.)
A pun is a play on words based on the similarity between two words, usually in their sound or spelling.
Consider this old riddle (it comes from those ancient years of my youth when newspapers did not have color pictures):
Q: What is black and white and red all over?
A: A newspaper (it is black and white and read all over).
One of the greatest punsters of literature was William Shakespeare.
In the beginning of Julius Caesar, a shoemaker says that he may practice his trade "with a safe conscience" because he is "a mender of soles." This is a pun based on the similar sounds of the words sole and soul. Later, this shoemaker says, "all that I live by is with the awl." This is a pun based on the words all and awl (a sharp tool used by shoemakers).
Here's another Shakespearean pun, this one from Romeo and Juliet:
ROMEO: Give me a torch: I am not for this ambling; / Being but heavy, I will bear the light.” (light: brightness/weight)
Here, the pun is based on the two meanings of the word light: a) a source of illumination, and b) not heavy. Romeo is saying that he will carry the light (the torch) because it is light (not heavy).