Can I apply to SGU, Ross, AUC, Saba before finishing my prereqs.

yes you can apply to them if you have not finished your prereqs.

however you must have them finished by the time you matriculate.
so you need them before you start at the school. im pretty sure about this.

also check their websites for their exact policy usually under "admissions"

www.aucmed.edu
www.sgu.edu
www.rossmed.edu ?
good luck

You can being your applications, as goldfish85 stated, and you will be asked to add the necessary ducumentation as they become available.