Iris changes her iris eye color to brown, then a scene later they are blue again.
Sergey, a Russian, is interested in Joseph Stalin, but has a biography of him printed in English. That does not matter. Sergey speaks English. Being Russian doesn't mean you only have to have books printed in Russian.
Iris changes 3 parameters of her voice to command Josh's car to drive home, trying to match his voice. But voice biometrics is far more complicated than that, and wouldn't be thwarted simply by changing characteristics like pitch or tone.