If you want to delete multiple messages at the same time, hold down the Command key and select the items. Then, control-click or right-click any of the highlighted messages and select Delete.
To delete a conversation:
Safari Instructions
All replies. Deleting the thread or conversation just deletes it from your message app. Once someone respond to the text it'll pop up again. Leave the conversation means you're leaving the group thread and won't get anymore message from that group.
Restore a disk using Disk Utility on Mac
How do I recover a partition on my Mac's hard drive?
Choose Mailbox > Erase Deleted Items, then choose to remove them from all accounts or a specific account. For POP accounts, reduce the amount of time that copies of messages and attachments remain on the mail server before being removed.
How to delete on a Mac. Luckily, there is a very simple way around this problem. To make the backspace key act like a delete key, you simply have to hold down the fn (function) key in the bottom-left corner of the keyboard at the same time. Sorted!
The answer to your actual question is unquestionably NO. It will remain visible on another synced device until deleted from that device, and it may remain searchable via spotlight even after that.
Does the other person know if you delete an iMessage? Deleting your iMessage will not send any kind of notification to the recipient. They will not know about it and will still have a copy of your message and the original conversation.
WildSky said: Make sure Messages in iCloud is enabled on all of your devices. “When you delete a message, photo, or conversation on one device, it's removed from all of your devices.”
Tap the new Hearing button you just added. Select Headphone Accommodations, then enable Transparency Mode. Tap anywhere on screen to return to the Hearing menu. Scroll to the bottom of the list and tap Conversation Boost to enable it.
Delete your message history