I want to show only childs pages in all pages
$pages = \Ip\Menu\Helper::getChildItems();
echo ipSlot('menu', $pages);
Child items work for a selected page. You should define a parent.
Here's a definition of this function:
public static function getChildItems($pageId = null, $depthLimit = 1000, $orderBy = null) { ... }
If you don't provide any parameters, current page is taken as a parent and all its children are returned. This means each page will show a different menu.
Therefore, provide a specific pageId
to this function to make menu the same on all pages.
P.S. if you have some specific case, define it. Maybe it can be solved with different tools.