Birthday Culture

I have a general inquiry about how birthdays are treated culturally. (For young adults specifically)

Examples of what I mean:

In some cultures it’s expected that the birthday person is the one to provide cake/treats for everyone else (like at work) but in other places it’s everyone else’s ‘responsibility’.

Is someone’s birthday a day where they treat others or is it where others treat them?

Or like how if you’re given a gift, some places you're supposed to open it immediately in front of the giver, but others that’s rude and you wait until you're alone.

There’s nuance obviously but just generally speaking.

I would love any insight given.