If , then blocks. Then if , then is an atari, and then connects.
togo: This obviously only works because there is an additional freedom at a.
The tricky move is . However, solves the problem. Subsequently, if White a cuts the Black stones, then the atari at b transposes back to Variation 1.
The Black move at is a mistake. Now, after , Black cannot avoid the ko at a. Even if pushes, can block, and then a Black move at b will be self-atari, so the ko still cannot be avoided.