To jump "somewhere", just use an Alias:
http://www.concrete5.org/documentation/general-topics/site-tree/...

However aliases don't work inside a parent-subpage-relation! For your first example go to
http://www.concrete5.org/documentation/how-tos/editors/built-in-att...
and read the section about "replace_link_with_first_in_nav" attribute.

For your second example you could use an external link, linking it to the url of your "blog" page. (But do you really need this?? The navigation path to the parent level should be intuitively given by a well formed menu!)