Can someone breakdown the movie Sucker Punch for me?

Okay I just got done watching the 2011 movie sucker punch and I am so confused!! Is the mental institution really a front for a prostitution place? If not then why is the main character dancing to distract people? How did she kill her sister? And why was that main evil guy forging the counselors signature? And what did the stepdad pay him for? Can somebody please answer my questions and then some cause im confused. A break down of the movie from start to finish would be really great thank you