1) for those who doesnt have finance background, i recommend take it in order.
2) prm syllabus updated once in 2008, for future update, you will need to email prmia for answer.
3) yes, you can register as free member. However, sustaining membership give you discount for exam registeration and study material, so it is wise to register as sustaining member so you can enjoy the discount and material such as webinar.