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: August Ames, Aaliyah Hadid, Lana Rhoades, Little Caprice, Gabbie Carter, Tori Black, Azul Hermosa, Kali Roses, Kimmy Granger, Janice Griffith, 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.