We would like to know if a given user has enough rights (permissions) to browse a given node and make sure this node is a descendant of his Start Node (User settings).

After investigating a little bit, it seems that there is not a common way to achieve this. There are some methods in the Umbraco core libraries but they are "internal" or "private".

Is there an API or a recommend way to do this, or we should create our own method?

When we changes the permissions in order to avoid a user accessing some nodes, these changes are not applied immediately. It seems they are cached. Is that normal?