You can change your chat username by selecting the "Change Chat User Identity" button that is located at the top of the page once you are in a chatroom. A popup will appear allowing you to change your chat identity. Make sure to select Submit after you have modified your chat name.

Yes, you can view the chat archive to view previous chat sessions. Select the archive button next to the chatroom you wish to view. It will list all active sessions by date and time. Select the appropriate archive.