This should actually be able to be switched off in the settings. Under "Always on display and lock screen" there is a setting "Pick up device to wake up". This should be set to Off. In the same menu further down, there is also the pocket mode, which should be switched on.

Unfortunately, I don't know 100% about Whatsapp, but the "Allow notification badges" switch should be switched on in the Whatsapp app info under Notifications, Settings. But that didn't work for me either sometimes. Badges are these small numbers that can appear on the app icons.

If a cover with a lid is used, there are some that switch on the screen when you lift the lid in front of the glass. The function should also be able to be switched off. If the power button is pressed and the phone is off, it won't just turn on in the case unless that ambient display stuff is active where it keeps showing a time. That could cause these problems. Since the phone has an AMOLED display, this function should also be on. But this can also be switched off. Then the problem should be over. Simply switch off everything that still shows anything on the phone when it is switched off, no clock, no weather, nothing :).