Turn off mobile data and wi-fi on punting phone, can't report anything then.
Also Jailbreak / rooting is required for non OS apps like whatsapp, viber, gmail etc.
Storm in a teacup
I think you are way off there mate. If he turns off both wifi and mobile data then he can't actually use much on it can he? And if the program is a key logger or call recorder it would make no difference.
Rooting is of course not a requirement for apps like whatsapp viber and gmail. They are among the most common apps on the planet and it is not worth anyone's while to block them.