No.709(Answers)

Black 1 is crucial.
If White 2, Black lives with 3.
If White 2 at 3, Black lives with 2.

Black 1 is wrong.
With White 2 and 4, Black dies.

Black 1 is crucial.
Black lives, and White dies.
If White 2 at 3, Black 2 kills White.

Black 1 is wrong.
With White 2 and 4, BLack cannot win unconditionally.