What is a research student?
I've only encountered the term "research student" in Japan (研究生), most (all ?) graduate schools in Japan offer it (see for example the Graduate School of Information Sciences of Tohoku University). As I understand it


A student will apply as a research student if they wish to conduct research at the university under the supervision of a faculty member, but are not interested in taking classes or obtaining a degree. You could want to do this for example as a "gap year" between undergrad and Master's (or Master's and Ph.D.), this could be a way to get some research experience under your belt, and perhaps improve your application for Masters or Ph.D.
Anything goes, as long as it is agreed between the student and supervisor.
You are not required to present anything. Since there is no degree to be obtained, there are no requirements to be fulfilled.
is subjective.