Is it possible, during an imaginary period, to contact a crew member for assignment of a service, whose beginning is outside the periods of the scheduled imaginary and mediating a period of rest?

The standard defines “Imaginary” as: period of time defined and previously notified during which the crew member must be available to the operator for assignment of a flight, positioning or other activity, without a rest period, as follows: 
(a) imaginary service at the airport: waiting at the airport that can lead to a service assignment; (B) another imaginary: provision of imaginary at home or in adequate accommodation, which can lead to a service assignment. 
 
The fact that in an imaginary you can assign flights, positioning or other tasks without a rest period does not mean that you can not also perform a task assignment or change the subsequent schedule.