Is Dialogflow part of Google cloud?
This is a Dialogflow-specific extension of the Google Cloud $0 trial.
What happened to Dialogflow?
Google bought the company in September 2016 and was initially known as API.AI; it provides tools to developers building apps ("Actions") for the Google Assistant virtual assistant. The organization discontinued the Assistant app on December 15, 2016. ... In November 2017, Dialogflow became part of Google Cloud Platform.
Can I use Google Dialogflow for free?
While use of the Dialogflow Trial Edition is free, there are limits on the amount of requests that you can make. For details, see Quotas & Limits.