With this multi-step form, the user should have the opportunity to save each intermediate step (draft) and not just at the very end. The user should be able to cancel the process without saving and he should go back and forth. The fields on the first page are mandatory to continue. Some of the other fields are mandatory in order to get out of the draft status.
What would the correct hierarchy of buttons look like? If you can't take steps forward or back because you're on the first page or the last, would the button disappear or just be grayed out? When he disappears, the buttons jump back and forth, which I don't like.