The 1-2 point is the key in the solution.
If here, then Black can play
and
and capture White due to shortage of liberties.
attempts to set up a ko fight. However,
connects to the
stone and there is no ko.
and
lives too, but loses one extra stone.
and
is greedy. After
makes the large monkey jump, Black dies of a straight three dead shape.
here cannot live.
simply plays a honest move, and Black is a L-group dead shape.
Because Black lack outside liberties, is possible. If
blocks, then
onwards cause Black to be trapped in a double damezumari.