1. Answer: It depends on everyone's taste and these rankings change all the time. According to RankMyPorn, at the moment, the top ranked Under 25 Female Pornstars in the world are: Lana Rhoades, Sasha Grey, Aaliyah Hadid, Christy Mack, Devyn Cole, Pepper Hart, Quinn Wilde, Peta Jensen, Riley Reid, Kali Roses, but these will change based on what people vote.
2. Answer: It changes. You can see the latest rankings on RankMyPorn.com and also vote on it for free.