"I've often found in old books that instead of saying 'twenty-four' they used to say 'four and twenty', when did they stopped doing that and switched around?
Was it only used for someones age (the last time I read it it was about someones age, can't remember the other times)?
Was it used with other numbers, like five and thirty or something?"
The history is (as Amava said) that some languages do assemble numbers like that. For English, it's either a Germanic speaker directly translating or a change of word order to fit the meter of a poem or song, or a figure of speech like the twist used in the Gettysburg Address.
"How exactly does layaway work? Wouldn't it just be more effective to save up and go buy the items? Do you get your money back if you change your mind?"
The main reason to buy something on layaway is to make sure it doesn't sell out before you can afford it. And in most places, layaway is a delayed purchase, where you don't get the item until you've paid the full price, so most places can handle "returns" if you decide you don't want it after you've paid part of it. There will usually be rules about forfeit in the case of clearance or seasonal items and such, but most of the time they can just reshelve it (it never left their possession so it's still new goods) so they'll give you back what you paid in, minus the fees, if you change your mind.
"Why do I still have the strong urge to do some things I'm advised not to do?"
I don't know, but whatever you do, don't try to look up "reverse psychology".