Setting Up RATS

when setting up a rat to hack over the internet so WAN is it still necessary to port forward if the victim downloads a client that is sent to them..I was always under the impression that if a client to them and they download it portforwarding isn't necessary...

Question # 2 is port forwarding only necessary when behind a router? if I am connected to the internet with a ethernet cord would I need to port forward and how would that be possible?? thank you and sorry for my spelling