> create groups, name them, invite and kick out other kids at will, and send messages + audio/video.

All of that has been (and still is) available on everyone's phones since the dawn of time except for "name them": https://en.wikipedia.org/wiki/Multimedia_Messaging_Service

  - create group: send an MMS message to whoever you want in the "group". Now you have a group chat.
  - invite people: send a new MMS message including all past participants and the one additional participant.
  - kick them out: Send a new MMS message including all past participants except for the person you want to remove.
  - send messages + audio/video: MMS supports all of this.