Here’s how message reactions will work in WhatsApp - Android Authority
Interestingly enough, the source notes that users can only react to a message once and that there are six different emoji to choose from.So those hoping for a wide variety of reaction options or even custom reactions might be disappointed (although custom stickers are a welcome addition this week).
We also get a peek at a screenshot (seen above), showing that users will be able to view all reactions to a message or filter them by a specific emoji.