You can tell you're sending RCS Chat messages when the input dialog box says Chat message or RCS message. If Google Messages doesn't prompt you to turn on RCS Chat, follow the instructions in the ...

Google Messages for Android will soon let users delete a chat message for everyone in an RCS group conversation.

After seeing it in testing earlier this year, Google Messages has widely deployed the ability to delete RCS messages from recipients' devices.

Feel free to try and delete a message from a group to see if you are presented with the screen above. And if not, you may need to join the Google Messages beta, which we’ve linked to below.