Thank you! Act 1 is the first part concerning child Sarah, act 2 is the part concerning teen Sarah and act 3 concerns Billy and Adult Sarah which you got to meet very briefly at the end of act 2. Act 3 gets a "title screen", act 1 and 2 will have one each as well at some point. Necrovale is great btw, I don't think you will be disappointed .
Those songs are not remixes btw, they are covers ;). Nothing was sampled.