Y'all is rather colloquial American English and caused me some confusion, as a native English speaker I would like to have the option of using the words you and all to answer this question :-) thanks
what's the difference between para and pra?
They're the same, "pra" is just the informal - and I'd say more common, daily used - version of the correct, formal "para".
Exactly. And do not use pra when writing.
why vocês and not você?
Both should be accepted.
what is the difference between vocês and você?
"Você" is singular and "vocês" is plural.
Duo translates this to "It isn't late for you." I think I forgot something. Does the "Não é..." ever translate to "No, it is" (as in "No, it is late for you")? I expect it doesn't, so what does?
= Não, é tarde para você.
Does this also mean 'it's not too late for you"?
Can this also mean: It isn't afternoon for you.
Like in a situation where you are talking to someone from another country on the phone, and then you remind yourself that even though it might be afternoon where you are, it isn't afternoon for them.
I think it should also be accepted for this context.
Para=to por=for therefore Não é tarde POR vocês. Explain why this is wrong please