sinantos:
At the end position the other hane also works since the position is symmetrical. However, only one hane is accepted as correct.

kovarex:
Ok, I consluted with another strong player and I made this change: I added 10 000 years ko as a special status, and it is considered to be the same value as -1 move approach ko. I changed this problem to be status based, and this result snow in both 10k ko and 1 move approach ko to be both solutions.

kovarex:
I made corrections to this problem: 1) I took some idea from other internet source: https://www.go4go.net/go/carpenter_square_10 And realized that the 10 000 years ko (which I actually tried to do when returning to the problem), shouldn't be marked as incorrect. Currently I believe, that the 10 000 years ko is the only and best solution, as 10 000 years ko seems to be better then 1 step approach ko, as 10 000 years ko can be directly change to 1 step approach ko at any time the attacker wants, but 1 step approach ko is played right away. So I marked all 1 step approach ko variants wrong, and kept the 10 000 years ko variant as the only correct in this problem. I'm open to feedback!