Programming puzzles: processing lists!

[Han]

#13 is not clear to me -- what is meant by:

"verify that the list is made up by two identical (also the order) sublists. Return the number of sublists if valid, "invalid" otherwise"

If the sublists are identical then wouldn't the original list simply be generated by a single sublist? What is the significance of having two identical sublists? Also, should the program always return the largest proper sublist that generates the original list?

{ 1 2 1 2 1 2 1 2 } can be generated by { 1 2 } or by { 1 2 1 2 }; should the answer be 2 or 4?