Child theme does not include any files from start, just styles.css and fucntions.php. If you need to overwrite any files there you could copy them from parent theme to child theme keeping the folder structure. Don’t copy files from the framework folder. If you need to overwrite function from file of the framework folder then copy only function to child theme functions.php and edit that according to your needs.
About breadcrumbs. You can copy header.php file from parent theme to child theme but we don’t show breadcrumbs in the header.php. Breadcrumbs code is at xstore/templates/breadcrumbs.php Anyway you did not provide code that rank math gave you, you provided only comment.
Provide us with code that developers gave you and explain in more details what exactly you want to change in the breadcrumbs to point you to right way.
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.