Child theme loses functionality

I created a child theme for twentytwelve as advised and followed the directions. when I activate the theme, some functionality goes away. for example my customized menu bar goes back to the default of just listing the titles of every page on the site. I use Appearance – Menus to set something up and is has no effect on the website. I switch back to the regular twentytwelve theme and it works great.

It’s not worth it to make a child theme if I have to lose functionality, no?

Another thing I noticed, when I am on the child theme, and I go to the theme editor, the only thing I can edit is style.css. I can’t change any of the page templates or anything else, which I need to do. It says at the top right of the editor, that this is a child of the parent theme and I can click on the parent theme name and then I get all the pages to edit. But if I’m changing them in the parent, what’s the use of having the child theme at all?