For question 5, I said that 2 and 6 would have to be in a row and column with another multiple of 2. If they were with each other, they would still each need 1 multiple of 2 to satisfy each row/column being a multiple of 4. However this is done, there will be at least 1 row without a multiple of 4. E.g.
2 6 - (12)
4 - - (4)
8 - (8)
(8)(48)(-)