Once set up with apache web server, can svn be accessed over the internet or only within a local network?
It can be accessed through the internet, as long as there is not preventing it, such as a firewall.
It depends on the configuration of your network and your server. If your machine is otherwise accessible from the Internet, then your Subversion server will be, too.
Yes, but beware of the security issues that comes along when you run public servers. If you only have it internal on you own network it is not exposed in the same way.
If this site can't see it, the net can't see it.
Are you trying to make your repo world readable, world read/writable, or internal only?
You should also consider accessing subversion through ssh as a possibility if you need connectivity over the Internet.
More information http://svnbook.red-bean.com/en/1.5/svn.serverconfig.overview.html