I developed a chat application (Android platform, native Android development) using asmack library. Also I have a task to create from the application group in openfire server. I don't know how to do it.
And also additional question: is it possible or not?
You could use the Openfire REST API plugin, which allow you to create new groups over REST/HTTP e.g. from your application.
Look here: https://www.igniterealtime.org/projects/openfire/plugins/restapi/readme.html#create-a-group