Difference between messages : 'server returning 404' AND 'No route found for GET /routeName - symfony

Question

windows 8. symfony 2.7 installed with default settings on d:\htdocs\sym\again\blog\
With apache, running the URL: http://localhost/sym/again/blog/web/hello , returns the following error:
Oops! An Error Occurred
The server returned a "404 Not Found".
Something is broken. Please let us know what you were doing when this error...
INFO: The above error is different from regular apache 404 'object not found' message. for http://localhost/NonExistingPage
With the built in PHP server php app/console server:run,
running the URL http://localhost:8000/NonExistingRoute returns
No route found for "GET /NonExistingRoute" 404 Not Found - NotFoundHttpException 1 linked Exception: ResourceNotFoundException »
while running the URL http://localhost:8000/hello, returns the actual page.
Question: What is the different between the errors ? My understanding:
the regular apache error is simply when a file is requested that is not found by apache
The 'Oops! An Error Occurred The server returned a "404 Not Found". Something is broken' is what is confusing me, I don't understand why/how it is different from the route not found errors.
the route not found means that it reached symfony but did not find any route matching /NonExistingRoute in the routes file.
Another Strange thing:
if routing.yml is changed to:
offtopic_books_homepage:
path: /sym/again/blog/web/hello
defaults: { _controller: OfftopicBooksBundle:Default:index }
then
http://localhost:8000/sym/again/blog/web/hello - returns the expected page. (with app/console running)
Whereas
http://localhost/sym/again/blog/web/hello - gives the following error:
Oops! An Error Occurred
The server returned a "404 Not Found".
Why ?

Answer 1

In this case please reset cache for prod env:
php app/console c:c -e prod
Note:
Please use dev env and app_dev.php for development, not production environment.