What are the rules for a back story?

Polaris Polaris had a very easy and nice childhood. She got everything that she wanted and nothing would ever go wrong. All she knew was happiness. That is until her parents fled the country and left Polaris behind. She was only thirteen and had no idea what to do. For the next nine years, she spent at friends houses or at hotels. She went wild for those nine years. She found herself in northern Canada. She had been born in Toronto and was not used to this cold. She adapted quite quickly. She is now traveling the globe searching for anyone who knows anything about her parents. She is trying to find hope.