Unfortunatelly WhatsAp has not the option of being offline. You will receive messages 24 hours even while you are sleeping, working or whatever. That can be really disturbing. With WhatsAp Offline you will appear offline in 3 easy steps. While you are offline you won't be able to send or receive messages.
Allows the application to access the phone features of the device. An application with this permission can determine the phone number and serial number of this phone, whether a call is active, the number that call is connected to, ect.
prevent phone from sleeping
Allows an application to prevent the phone from going to sleep.
automatically start at boot
Allows an application to have itself started as soon as the system has finished booting. This can make it take longer to start the phone and allow the application to slow down overall performance of the phone by constantly running.