They break rules and don’t know why.
Children this age generally want and need rules, but they also break them from time to time. They rarely know why they do it. Sometimes, they are actively confirming that the rule exists. Other times, they simply try to follow rules and fail.
What you should do: Be firm and matter-of-fact when setting rules. Don’t punish your child if you think she broke a rule accidentally. Don’t take for granted when your child does follow rules, and compliment her.