most students, most of the students . only these phrases r correct.
the 2 other phrse is totally wrong , and u cant use it in your senetenceeven on writting or speaking.
MOST OF THE STUDENT has the same meaning as MOST STUDENTS
in first one , before using this sentence , you should tell which student.i mean you had to speak about group of student and then chose some of them to seperate from the previous one.
ex
students in that class r very clever , and most of them do their home work on time.
(u see that in previouse sentence i ditermined the group of student)
but about second one = we use it in general sentences or when we want to speak generally
most of the student, around the word , have benn learning english since years ago.