It is now possible to message everyone in the messenger group at once. For that, Messenger has unveiled a feature like Slack at the Rate Every One.
This feature allows everyone in the group chat to be alerted if the rate is maintained. Now there is no hassle of mentioning one person in a group, now everyone can be mentioned at once. Messenger has also brought a silent feature in the app.
To use this feature you have to type Silent in front of your message and this will take you to sneak mode. This feature does not alert the user when the message is sent. These features are available on both Android and iOS.