is the vital point to live. After this, white has a few choices.
If white tries , black plays this way, and ends with a live shape.
If white tries this , black needs to be a little bit careful. Black can capture three stones because of oiotoshi.
In response to , this ends in disaster:
It seems to work, until one sees the under the stones tesuji.
If here, then kills. Black cannot play at a due to shortage of liberties.