What I'd like is that the only method of navigating is through Previous and Next. I'm concerned that a candidate may get confused and accidentally skip a question. By limiting it, they cant, for example, answer 1,2,3 miss 4 and end up getting a lower score.
I also think these navigation links crowd the page too much and I want it to be as simple as possible:
Would look better as
Even better would be if Next and Previous were submit buttons