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How is it a unique rectangular and how does not placing 1 or 8 in yellow cells make a deadly pattern?

There are many 3s and 5s around and there are few places to put the 1s and 8s in row 9.

Similar to the BUG, if the yellow cells did not contain 1 or 8 they would both contain 35. As in the BUG situation, it would look like the puzzle might have two solutions by swapping the 3's and 5's in the green and yellow cells, but since we know that the solution is unique, both halves of the two solutions must be invalid. You can read about Uniqueness patterns and the BUG principle, for example, here.

Leren