How to Disable External DNS recursion?

I know that to disable recursive queries in BIND, I need add the following lines to the options section of /etc/bind/named.conf.options

allow-transfer {“none”;};
allow-recursion {“none”;};
recursion no;

Will the above configuration disable all DNS recursive queries?

How can I disable DNS recursion only to external network queries and keep recursion only for Internal network?

If I disable the recursion, then what process will be performed by the BIND resolve the name request? Iterative or Inverse?