1) You can't read the police statement in court unless an attorney gives it to you to read on the record. And even if an attorney does, you'd still have to answer any other relevant questions.2) You can be prosecuted after testifying if you say anything that  provides reason to believe or evidence that you committed a crime, unless you had some sort of immunity (i.e. can't be prosecuted for what you testify) deal in place).3) You could be asked questions not directly about the case if they are nonetheless relevant to it, such as about your cell phone plan, where you get your cell phones and what you pay for them, how you know the acquintance, whether you've done business with him before in other contexts, etc.