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 30 Female Pornstars in the world are: Mia Malkova, Kayden Cross, Katrina Jade, Eva Angelina, Rachele Richey, Monique Alexander, Madison Scott, Rebeca Linares, Katie Morgan, Ashly Anderson, 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.