This question is actually three questions, but since they are all related to each other, they should stay in the same question.
First, should I allow a user to change the url of a already created page?
I've been working with Drupal, and Drupal allows the user to change the url, but if someone has that page bookmarked, it redirects to a 404 page, so there is no mechanism in place to accommodate the url changing.
Second, if I allow the url to change, should I deploy any kind of mechanism to redirect automatically in case an old url is used?
And third: Let's say for example I have the following structure on a site, with the following pretty urls:
When I change the url of page-1 to for example: products, should all child pages change their urls to accommodate the parent page change?