1) Require php modification
2) Meta info from plugin?
Both of the above comes under custom work and charged separately. To discuss contact us via contact form.
3) To learn about child theme refer: https://developer.wordpress.org/themes/advanced-topics/child-themes/
A sample starter child theme is already available in member area. For eg. if a file with same name is present in child theme, front end will load content of that file first rather than from parent theme.
Child themes are for advanced users and can be used when you have a lot of php modifications, mostly if you are hiring a developer to customize a theme.