One of my secondary characters had a birthday today. (First one since starting the game) I got the cupcakes and I know they can be kept or given away. The first person I saw was Tangy, who when I talked to, said "happy birthday" and I had the option to "give a cupcake". She gave me birthday candles in exchange. When I talked to Carmen (who hosted the birthday party), she didn't mention the birthday and the gift option was the typical "do you want this?" I didn't give her a cupcake. So, can I tell who will give me birthday items based on the dialogue? I have no idea what the friendship levels with villagers are because she's not my main character and it's not something I've actively worked on.
You can count the ones who were at the party out, since I think they snagged some from the piñata. Plus, they already gave you a gift. My birthday was back in May, so I might not be remembering correctly, but I gave away all but 1 to the rest of my villagers. I decided to keep 1 for decorating, so next year I'll give them all away.
I think that after you give a cupcake, they stop asking about them, so you can only get the prompt once.
I think it depends on their friendship level with your character. On my second character’s birthday she gave out all the cupcakes, but didn’t get any birthday furniture. She only got random furniture and clothes.
As was said above, if the villager was at the party then they won’t offer a birthday item in return for a cupcake. I have no idea if friendship affects it unfortunately - I’m fairly certain I got gifts from all my villagers, but that was with my island rep and I have at least some level of friendship with everyone
