technically, an undergrad degree isn't required, only a handful of courses
whether you'd actually get admitted without one is an exercise for the reader
whether you'd actually get admitted without one is an exercise for the reader
There are accelerated bachelors+MD programs that high schoolers can apply to; these would shave off two years of overall training time. Notably, despite being accelerated programs, these grant a bachelors degree before program participants advance to medical school.
EDIT: I'm aware that this used to be the case but I don't believe that any schools still allow this.