Is it possible that the number of patterns for drawing a loop is more than one?
No, only one possible way how to place entire loop.
Is a row or column without clues required to be empty?
In the example, the only row without clues is entirely empty, but the puzzle is unique even without that assumption.
In the competition puzzle, all rows and columns have clues.
Japanese Sums and Loop
No, only one possible way how to place entire loop.
Japanese Sums and Loop, unclued rows
Is a row or column without clues required to be empty?
In the example, the only row without clues is entirely empty, but the puzzle is unique even without that assumption.
In the competition puzzle,
In the competition puzzle, all rows and columns have clues.