The theme background color and image can be changed within the WordPress Appearance options for all of our themes.
Yes, you can modify them as much as you like.
This is an option with all our themes. The logo can easily be changed within the Appearance > Header section, or the Appearance > Customize > Logo section of the WordPress dashboard, depending on your particular theme.
Yes. We always keep our themes up-to-date with the latest version of WordPress.