Of course no two boxes contain the same number.
No two Boxes contain the same number?
8. Once and only once?
15. One and only one column?
16. Do you mean exactly two times? To prohibit having 2 sixes and 3 eights?
17. The five column sums share one and only one prime factor?
18. Once and only once?
Then, if CL is 45 then 50-59 do not appear in col D?
19. Major diagonal?
Clue8: Yes, once and only once.
Clue15: Yes, one and only one column.
Clue16:In each column there is one and only one numeral that appears two times. other numerals could be one or three or more times. So the condition of this clue cannot prohibit double digit numbers, at any space in the table.
Clue17: there could be more than one prime factors for the sums of different individual columns, but there is one and only one prime factor which is common to all sums.
Clue18: you are absolutely right, if CL is 45 then 50-59 do not appear in col D?
Clue19: Yes, we are talking of the major diagonals.
I think I have clarified all the doubts...?