What context do you need? This boy is the first boy, that boy is the last boy. They could be in a queue for something, they could be getting one on one training at the gym and the trainer wants to go home, they could be kids after a birthday party being picked up by parents, it could be a reference to a bag of jelly babies (don't worry if you don't get the reference, you probably wouldn't be asking the question if you did).
The context doesn't matter because there isn't any context in which the translation would be different.
It's not the translation I'm worried about, I can translate the weirdest shit, I promise. I just couldn't imagine a situation where a string of words such as this would be uttered. (Even in the situations you mentioned, I can't see myself saying this exact thing, but each to their own, i suppose)
I like to think of a mystical fantasy book where the bad guy is searching for the last boy of his kind! The last dragon rider like eragon or i am number 4... Although number 9 would be last. And the bad guys go around in gruff voices asking "do you have the last boy" when they enter the town the main character is hiding in before the movie scene changes for suspense... Hope that helped a bit, if i look like a complete doofus so be it
This sentence bugged me since i saw it and so i went to a friend who says it literally translates "Are you the last boy?" So this is wrong.
Your friend is wrong. "Are you the last boy?" is a copula, liking the pronoun "you" and the noun "boy", and therefore the dependent form of the verb bí would not be used.
An bhfuil an buachaill deireanach agat? - "Do you have the last boy?"
An bhfuil an buachaill deireanach leat? - "Is the last boy with you?"
An tusa an buachaill deireanach? - "Are you the last boy?"