Note that the option of creating new apps with the Ionic 4 framework was removed and we no longer support the projects that were created with it earlier.
Moreover, you are free to effortlessly migrate your Ionic 4 project(s) to their Ionic version with keeping both apps active.
Please check this page to learn how to do it.
This section includes step-by-step tutorials with examples of working code.
Many of them can be created from backups and then browsed, run, or modified to get an understanding of how everything works.