You can delete messages for everyone or just yourself.
Deleting messages for everyone allows you to delete specific messages you've sent to an individual chat or group. This is particularly useful if you sent a message to the wrong chat or the message you sent contains a mistake.
Messages you successfully delete for everyone will be replaced with “You deleted this message” in your individual chats or groups. Similarly, if you see “This message was deleted” in an individual chat or group, it means the sender deleted their message for everyone. Please understand that if you or your recipients aren't using the latest version of WhatsApp, this feature won't be supported.
Deleting messages for yourself allows you to delete your copy of messages you've sent or received from your phone. This has no effect on your recipients' individual chats or groups as they'll still be able to see the messages.
Note: Deleting multiple messages at once isn't supported on KaiOS.