Apache Nifi Enterprise support and license

[#1]

Do we have  to take any kind of licences, when we  use Apachi Nifi at enterprise level?

How securely we can use it for finical data at client environment?

What kind of data transformation does NiFi and Spark combination supports? Does only supports Streaming data ? or it also supports historical big data?

How is to integrate NiFi and Sprak?  two communication is possible?