Answer 3
Pages in a site (non-publishing) can use different master pages and this can be set using SharePoint Designer. A page can have one of three master pages assigned to it in this manner. you can attach it to the default.master (system master) page, the custom.master
(site master) page or a specific master page of your choosing. If you attach it to either the default or custom master page, the master page being used can be changed via the GUI by selecting a different site or system master page. This is possible in the
GUI only if Publishing is enabled at the Site Collection level. Page layouts are a different breed, however, and all the layouts in a specific site will use the same custom.master (site master) page. this is something you cannot change on a layout by layout,
or better yet, layout page by layout page setting.