Most Welcome,

I have seen your screenshot as the icons missing on that specific page. You need to make sure that you are using https not just only http in that page permalink.

Also the WordPress Address (URL) and Site Address (URL) must be the same from Settings >> General.

1) Child theme is mostly used for customization purpose. So you can customize your theme and the changes will not lost after update.

2) Child theme should be activated if you want to customize the theme.

3) Yes, all the changes will be lost after update if you are using parent theme. But if you use child theme those changes will not lost after update.

You don’t need to create child theme from scratch because we already made it for you (you have found in theme package downloaded from themeforest). Here is the link that demonstrate how it works: https://developer.wordpress.org/themes/advanced-topics/child-themes/

Best Regards.