If you want to become a Registered Practitioner, you MUST sit the Foundation and then the Practitioner, in that order.
You can sit both exams in the same week or even day, or you can split them and sit them months (or even years!) apart.
If you pass both examinations in the same week, you will receive a Practitioner Certificate but not a Foundation Certificate - as you cannot sit the Practitioner exam without first having passed the Foundation, it is not necessary to send a separate Foundation Certificate.
You do not have to take a course to sit the examinations - it is down to your personal preference.