I've been controlling for 26 years all around the world and....
On initial contact if I tell an A/C that they are "Identified" I dont expect an acknowlegement although they will sometimes say "ABC, Roger".
If I say "no radar contact" then I expect normal position reporting from the pilot until they become "Identified".
If I lose a target and advise "Radar services terminated" then I would expect some acknowlegement, "ABC, Roger", whatever, indicating that from that point onwards the pilots would resume position reporting.
Hope that helps, your operator may have their own rules, as may your local ATC unit.