Adding custom fields to bbpress reply form

Referring to post “adding-custom-fields-bbpress-topic-form” with link https://wp-dreams.com/articles/2013/06/adding-custom-fields-bbpress-topic-form/,
I want to add custom fields to bbpress reply form accordingly.
I only altered several key words from “topic” to “reply”. And I also tested more hooks to trigger the function. However, I could not show the related field after testing a test reply.
Here is the code:

Please kindly give suggestion. Thanks!