How to set up sending messages to actions in the Vkontakte group?

Question

API

How to make a person who has performed an action in a group (liked, reposted, left a comment, posted a post, posted a photo, unsubscribed from the group) received a message from the group (given that he has allowed messages from the group)? What should be the script?

Answer 1

https://vk.com/dev/callback_api
https://vk.com/dev/messages.send