Availability Group configuration & licencing
In order to redirect reporitng app or application with only read only queries you need to specify read only intent in application connection string (web.config or app.config in case client application is .NET)

The below is excerpts from SQL Server BOL 


  The application intent connection string property expresses the client
  application’s request to be directed either to a read-write or
  read-only version of an availability group database. To use read-only
  routing, a client must use an application intent of read-only in the
  connection string when connecting to the availability group listener.
  Without the read-only application intent, connections to the
  availability group listener are directed to the database on the
  primary replica."


Regarding your second question, if network throughput between two DC is OK you should be fine. 

As long as any secondary replica is only solely used for DR (disaster recovery) and does not perform any work like read only request or backup you do not need to license it.