Entity_alias and token create

one of the options when creating a token is using a role and specifying an entity_alias

entity_alias (string: "") > - Name of the entity alias to associate with during token creation. Only works in >combination with role_name argument and used entity alias must be listed in ?>allowed_entity_aliases . If this has been specified, the entity will not be inherited from the >parent.

is the entity_alias “name” unique across all entities and aliases ? If not, what is the name ?

Another question I have is regarding policies. If I use entity_alias on the token, I would expect to see the entity + group policies of that entity being used . Is this the case ? I seem to be getting the parent token policies