no, the next section doesn't start until you click "next." so you can theoretically sit at your cube for ages until you feel like starting the next section.
i realize that it's all subjective, but my personal opinion is that the PS was easier, the VR was average, and the BS was harder than the AAMC exams i've taken. hopefully this translates into a predictable score! some of my bio passages/questions were verbal-ish, in the way that they were difficult to read, and involved flipping around experimental data in a +/- fashion ("which of the following would LEAST support the thesis that so-and-so was NOT responsible for such-and-such?")
btw, my PS involved the spaceship-tether and thigh-calf problems; the VR included the soccer, lit. crit., hudson river society, T rex, irish bridges, & language development; and the BS included passages on a couple climbing a mountain, the cell differentiation passage that everyone seems to hate, cholesterol, transcription factors/lung cancer, a passage about hydration levels and how they affect various bodily states, one about a strep +/- bacteria experiment, and an ochem passage about amino acids and their drug derivatives that threw me for a loop. usually i can count on ochem for some easy points, but today's ochem was strangely hard.