① The median of this set of data is (92+93)÷2=92.5.
② The mode of this set of data is: 98.
③ The average score of the midterm math test in this group is: (81+84+86+88+91+92+93+95+98+100) ÷12 = 92 (score)
More than 90 points are excellent, and 8 people have excellent grades.
So the answer is; 92.5,98,92,8.