WhatsApp does not provide an option to make a received message appear as "Sent" but not "Delivered" without actually reading it. Additionally, you cannot delete someone else's WhatsApp messages for everyone unless you have certain administrative control over a group chat. WhatsApp's message deletion feature is designed to allow you to delete messages you've sent, but it won't work for messages sent by other users.
Here's what you can do:
Read Receipts: By default, WhatsApp sends read receipts to the sender when you've read their message (indicated by two blue checkmarks). If you don't want the sender to know that you've read their message, you can turn off read receipts in WhatsApp settings. Keep in mind that this will also prevent you from seeing when others have read your messages.
Ignore the Message: You can simply choose not to open the message and leave it unread. The sender won't receive any notification that you've read the message until you actually open it.
Mute Notifications: If you want to avoid being disturbed by notifications from this person, you can mute the chat. This will prevent new message notifications from appearing, but the messages will still be delivered.
Block the Contact: If you don't want to receive messages from this person at all, you can block them. This will prevent them from sending you messages or seeing your online status.
To mute a chat, you can do the following:
On Android: Open the chat, tap on the three dots in the top-right corner, select "More," and then choose "Mute." You can specify the duration for which you want to mute the chat.
On iPhone: Open the chat, tap on the contact's name at the top, scroll down to "Custom Notifications," and then enable the "Custom Notifications" toggle. From there, you can set the notification sound and vibration to "None."
To block a contact:
On Android: Open the chat, tap on the three dots in the top-right corner, select "More," and then choose "Block."
On iPhone: Open the chat, tap on the contact's name at the top, scroll down, and select "Block Contact."
Please note that while these actions can help you manage your interactions with the sender, they won't change the status of the message from "Delivered" to "Sent" or delete someone else's messages for everyone in WhatsApp.