GSATE problem 58

Hanmanchu: I'm really enjoying this book too, but struggling with some problems throughout the book.

That's why I have checking the correct answers with help of AI (ZBaduk / Katago).

The question (problem 58) is: How should Black reduce White's corner?  

The start of the correct answer is as follows:  

White can now descend to the bottom, in a variation:  

Following variation is given, but may be better:  

The following variation is not given:  

Continuation:  

Correct answer to problem 58  

The correct answer given in the book is still the best way to play, though.