In the very last reaction, don't acids open the ring so that it is attacked at the most substituted carbon? Why does this say its in base? Isn't it in H3O+ or am I missing something?
the grignard is a strong base. H30+ is going to donate a proton and cause the formation of an -OH group. Since the reaction involves a strong base, the least substituted product is going to form.
if the reaction occurs in an strong acidic medium, then the most substituted product will be formed