When chats are locked, the notification material and phone are hidden. The notification will display as WhatsApp: one new concept. 知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。 You may edit any message up to quarter-hour after sending, and it'll update for everyone from the chat. Edited messages should have the phrase "edited" close to https://apps-whatsapp.com/