Veritaserum and Imperius or memory charm

[Stray]

No: HPFGUIDX 126596


I was just wondering; if someone is under the Imperus
that instructs him to tell lies about something and
then is administered Veritaserum, which one is
stronger?

Alternative: what if the Imperius instructs the one to
believe that the lies are the truth?

And finally: what if there is no Imperius, instead a
memory charm that makes the one forget. Is Veritaserum
strong enough to call on the memories from the
person's subconscious?

ST