In this problem, White has to jump down at .
seems to be the strongest resistance. But with the exchange of and , is the standard way of killing. After , if Black a, then White b, the stone works perfectly, so there is no problem.
If here, then reduces the eyespace and proceeds to kill in the same way above. After , if Black a, then White b.
After , Black does not have enough eyespace to live with two eyes. There is no problem with the connection of the stone with the outside stones.
With the hane stone, the descent at no longer works. and is tesuji, so White can only create a ko with and .
White only manage to get a ko here.