Create online chat application

See top chat apps and features listed here:
https://www.zendesk.com/service/messaging/live-chat/?from=zp

I'm interested in my own top of the line chat app.
Including:
- freemium & premium versions.
- javascript to install on the clients site
- backoffice dashboard to manage chats
- android & ios management apps

Code must be written neatly and superb.

You must have previous proven experience with similar technologies.

features:
- Reach out in real-time with proactive engagement
- multiple admin users
- automation / canned responses
- Customizable branding
- Offline form
- Integration capabilities
- Routing
- Website visitor tracking
etc.