#1 Most medical students do not publish.
#2 Many medical students will dabble in one or several projects while in medical school.
#3 The most common publication that we see are case reports, followed by retrospective reviews.
#4 All programs see research as a plus. However, it is not of particular importance for the majority.
#5 While not strictly true, in general, the more competitive a program is or a specialty is, the more important research becomes.
#6 Research done prior to entrance to medical school is heavily discounted in weight. For many specialties, research is not just about learning how to perform research, but it is also an avenue to demonstrate interest in a particular field. In the surgical specialties, attrition is a real issue. Interest matters. Thus, for highly competitive residencies, it is typical for applicants to do research in that field during medical school.
As an aside, you seem to be struggling with written English in this thread. I would note that that will be a far bigger issue than research or no research.