RX, RX Advanced and all trial versions of RX use the same installer. So, the serial number you use to authorize the program will determine whether RX runs as a demo, full version or Advanced version.
Use the authorization menu to remove your current RX authorization, for example if you have upgraded to RX Advanced and have already installed the basic version. You may also need to de-authorize RX if you are using the RX trial version and wish to try the RX Advanced trial version. After removing your authorization, RX's authorization screen will pop up when you restart the program. Now you can re-authorize the application using your new serial number.