Sanjay_6 0 Newbie Poster

I had created a child theme. So i want to know some basic question about child theme.

1) i had create a child theme.If i am updating the theme, What should be happened ? I mean all customization which i had does manually is remain there in parent theme after updating the Parent theme.

2) After creating child theme i have to place all file of the parent theme in which i had made the customization in child theme or not ?

3) Suppose in child theme there are three files functions.php style.css screenshot

Now if i am activating this child theme is there any difference of look and feel of activating parent theme and child theme. i am asking these because i am facing these issues.

and i want to make sure for testing my child theme.