Being adopted does not change anything about your legal status as a minor.  You are an adult at 18, and are then responsible for your own needs and actions.  If your parents agree, you may move out earlier, but they are still responsible for you.  If you become emancipated then you can be considered a legal adult before you are 18, but this is difficult to do.   In Arizona there are no legal requirements and no way to establish that you are emancipated.  Other states may have different laws about this. 

A minor can be emancipated when they can and do support themself.  To be emancipated means to do all the things that an adult does for herself like: provide food and clothing, provide transportation to work and school, pay taxes, provide medical insurance for herself, etc.

The problem is that you cannot demonstrate that you can do these things if your parents don't allow you do move out and do them.