Is there any apps to lock my whatsapp and camera roll and other apps like fb YouTube etc ?

No. YOu can only lock your whole phone using a passcode.

You can put a passcode on your iPhone, go into your settings>general>passcode lock, You can take a look at this link for a photo vault app, https://itunes.apple.com/us/app/private-photo-vault-ultimate/id417571834?mt=8

But you can hide your chat scripts in the lock screen by following this: Setting->Notification Center->WhatsApp/Selected->Deselect "Show on Lock screen"