Is it about "para" and "por"?
In a sentence like this:
- Fazer para você
- to do something and give you the results
- to do you a favor
You are the "target" of something here
- Fazer por você
- to do something for you to like me (Duolingo's meaning)
- to do something because of you
- to do something in your place
You are the reason of something here
Because it's not in present tense. In present tense it would be: "Por você eu faço qualquer coisa"
"Faria" is "Futuro do Pretérito" (I don't know how it's called in English"). This tense implies condition. In this case, is something like "if you allow me, I would do anything for you". or "If you give me a chance...".
Another example: "Eu não faria isso se eu fosse você" = "I would not do that if I were you"