From a ‘secret chats’ function to using special ‘code words’ to jazz up your texts, these game-changing WhatsApp, iMessage, and Instagram hacks will revolutionise how you use your mobile phone, says an expertFrom a ‘secret chats’ function to using special ‘code words’ to jazz up your texts, these game-changing WhatsApp, iMessage, and Instagram hacks will revolutionise how you use your mobile phone, says an expert