IgoHatsuyoRonProblem122/Solution

First part - I  

First, white has to prevent both a (escape route) and b (killing the marked white stones) with a single move.

First part - II  

Now, the escape is prevented and black is squeezing the hell out of white.

Second part - I ( at )  

White couldn't cut at c out of shortage of liberties until now, but she has to find a way to do that (or live or escape).

Second part - II  

threatens capturing two stones. Black has to defend at , otherwise (at d) White ends with sente and five liberties, enough to cut at c.

Third part  

threatens to connect. prevent the connection, but now white can cut in sente, increase her liberties with (and due to ) and capture some stones connecting out.