1 - No sorting by date except in post view (which is ascending or descending, bottom right of page within the module). Users can also limit threads displayed in threads view by a drop down also in the bottom right view of the module (All days, last day, last week, etc.). Posts per page and threads per page are set by each user in their "My Settings" section. This is initial determined (and also set for anonymous users) under the Admin Settings of the module. 

2 - This works as the items described abovve. 

3 - I don't believe anything in the documentation explains exactly how search works. The content (body/subject) is searched via a simple like in SQL (This means your string must be found verbatim. In your example, searching for 5 documentation could return results because the order here). There are several reasons why search is not more robust in the module itself, but basically its how SQL handles searches WITHOUT the use of text-based indexing and the ntext usage for the body column).