I'm attaching some fake data I put together that match the description of your data. Given this, here's some code to answer your first question. The code uses basic MATLAB logical expressions, and so on. See if you can pull together the code to answer your other questions.
T = readtable('testdata.xlsx');
n = height(T); % total number of students
% #1
a = strcmp(T.Grad_Cohort, 'Fall 2020') & (T.Eligible_for_Diploma == 1);
b = sum(a) / n * 100;
fprintf('Percentage of all students in Fall 2020 cohort and eligible for diploma: %.2f\n', b);
% #2, etc.
% ...
Output:
Percentage of all students in Fall 2020 cohort and eligible for diploma: 14.29
