Can't get the joke 7 - out-of-bounds. The joke goes like: "What's out-of-bounds? An exhausted kangaroo!" What's the joke?

Can't get the joke 6 - statisticians. It goes like "If you laid all the world's statisticians end-to-end, they would still point in every direction." What does it mean?

Can't get the joke 5 - butter A: Shall I tell you a secret about butter? B: You'd better not. I might spread it. What's the joke? Thanks.

Can't get the joke 4 - irons. It goes like Boy: My mother and father are in the steel and iron business. Friend: Really? Boy: Yes, my father steals, and my mother irons. While I can understand that meaning "steals" while saying "steel" is kind of funny, I was wondering what is the meaning of "irons" here which make it a joke.

Can‘t get the joke 3 - pessimist. The joke goes like: What's the definition of a pessimist? A pessimist is a well-informed optimist. What's the joke? Thanks.

Can't get the joke 2 - "Alaska" The joke reads like 1st Eskimo: Where did your mother come from? 2nd Eskimo: Alaska 1st Eskimo: Don't bother. I'll ask her myself. What's the joke?

问题补充:

To Tom: That's the only text I read. No more context to give :)

Can't get the joke. I read a joke which goes like: "What did the traffic lights say to the car?" "Don't look now. I'm changing!" But I can't get the joke. Could anyone help explain it? Thanks.

what is a docket? I'm reading a dialogue in a textbook like this: "I'd like to return this address. I bought it here yesterday but it's coming apart here." "Oh, yes. I see. Have you got the docket?" "Yes. But I don't want to exchange it. I think I'd like my money back" I looked up the word "docket" in various dictionaries, but can't seem find a good meaning for the use in this dialogue.

问题补充:

This textbook is from Australia

Meaning of "Nothing the god of biomechanicswouldn't let you in heaven for‘ I read this sentence in a movie called "Blade Runner". It is said by a robot when killing his creator after the creator rejected his demand to give him more life span. I can't figure out the meaning though. Could anyone help?