SRM installation and license

Hi Team,

I am installing SRM for the first time and have few clarifications

1. In an environment with federated vCenter Single Sign-On domains, do not install Site Recovery Manager under more than one Platform Services Controller at the same time. What exactly does federated vCenter Single Sign-On domains means?
2. If I use the “vCenter Server with an embedded Platform Services Controller” at both sites. Can I use the  hostname of the vCenter server to Enter the address of the Platform Services Controller during the installation of  Site Recovery Manager Server
3. If I use the “vCenter Server with an embedded Platform Services Controller”  Is vCenter Server instance name same as its host name ?
4. Can I install the Site Recovery Manager enterprise in evaluation mode and configure SRM remote site? or License key is mandatory for  configuration? In SRM Document its mentioned “Site Recovery Manager Server requires a license key to operate. Install a Site Recovery Manager license key as soon as possible after you install Site Recovery Manager

Appreciate your answers

regards

Izhan