generally "ganar" means "win" and the reflexive "ganarSE" means "earn". Therefore, "...se habia ganado..." means "...had earned...." as opposed to " ...had won..." or "...had won herself....". There seems to be some argument about this, and even DL is not consistent, but "generally" this is why"se" is used here for "earned"....
Yes. There are two meanings for "to earn" in this lesson set. You can earn money or win a prize, that would be "ganar". Or you can earn love, respect, etc. That would be "ganarse". This is a shortcoming for Duolingo that the reason why these questions are being asked is not made clear. Earlier lessons have a hints section that you're supposed to read, but these later ones are without that. At this point, you have to do some sleuthing yourself or hope the distinctions are covered in the discussion thread. So, if you've found this explanation, congratulations, you now know the secret!
iirc for pronunciation accents are used when the spoken pronunciation doesn't follow the rules - one of which is that when words end in a consonant other than n or s i think, then the last syllable is stressed. The words you mentioned above are pronounced according to the rules & so accents aren't required.