P7A77: It seems there is death in the hane. This makes a and b miai. Other moves may be sente for black, but result in life for white.
here is a mistake: now white is alive.
P7A77: Black can't connect. If black connects with , the same
makes miai of the diagram's
and the marked space.
xela: Well, black can connect. It doesn't work, but neither does in your diagram. I'll add another couple of diagrams to show how the connection fails.