Min arrays containing all subarray symbol combos: De Bruijn sequences and tori

The subsequencecan occur in an even sequence.Only 104 of 432 unique 1-D 4-symbol every pair De Bruijn sequences are even.Are all possible 2-D 4-symbol every pair De Bruijn tori generated by this method? Question 2: For which positive integers R, S, m, n, k such that k > mn, R >=  m, S >=  n and RS = [Product from i = 0 to k-1]{mn-i) do there exist de Bruijn tori of the mn-permutations of a k-set? Question 3: For which positive integers R, S, m, n, k such that k > mn, R >=  m, S >=  n and RS = [k choose mn] do there exist de Bruijn tori of the mn-subsets of a k-set?

Source: web.archive.org