Incompetence is not non-compliance. ADHD is a disorder of inconsistency. It is not a time limited disorder. It is not determined by a single gene, but part of a very complicated system where protective genes may play a part. Biology is net necessarily destiny.
Child exerts great control.
The child needs to get 8 rewards to feel they are succeeding for every one taken away to fail. The best strategy is to use a full plate of rewards and encourage them to keep it rather than starting from 0. A possible strategy would be to give the full allowance and take away say 5 p for any of 5 rules broken. In the end, the relationship you have with your kid is the best predictor. Hope, encouragement and support are more important than Ritalin.