Unlike other instant messaging service, there was no concept of encryption when whatsapp was launched. Whatsapp launched its security update that makes the conversations encrypted on both the ends. Whatsapp encryption method is designed in such a way that except the people on the conversation, nobody can know it. It can not be hacked. But the question is, are my WhatsApp messages encrypted end to end if I use Older Version of Whatsapp messenger.
The answer is no. Even though, the feature is enabled by default in WhatsApp, Irrespective of your phone make and model (iPhone, Nokia Lumia, Android and Blackberry)The WhatsApp messages sent from older versions to latest versions or latest version to the previous version of WhatsApp are not encrypted. Both the user must have the latest WhatsApp version installed. Hope, this clarifies what end to end encryption means.
Can Whatsapp User SwitchOff End to End Encryption?
No. Users don’t have the option of switching off end to end encryption system.
Read: How Can I Turn Off WhatsApp End to End Encryption