Can editing functions.php of a child theme do everything?

Hej all,

In order to modify a theme, can I achieve it only by editing the functions.php of a child theme? I know that it’s recommended to use the functions.php of a child theme so that the theme will be updated and everything will be ok. So I wonder if there are some situations that you can’t do only with the functions.php of a child theme but have to modify php files of the mother theme itself.

I searched for this question a lot. But I couldn’t find any relevant answer.

Thanks.