Depends on when the offense was. Most probably not as you didn't commit the offense while you were on probation. Also, you may be able to file a motion to dismiss because of a delay or because of the statute of limitations.
Feel free to give me a call with any questions, I'd be glad to give you a free consultation.
Yes. A plea to a prescription fraud case does not exclude you from future probation grants. In addition, you may be able to argue that the District Attorney knew or should have known about the other arrest when making the probation offer to you. You were also placed on probation on one case after you were arrested for the other case, so the new filing will not violate the probation you are currently on.