I would like to ask you about backup. If I change new MacBook so Could I use old Agenda?
The easiest way to migrate your Agenda library from one device to another is to install Agenda on your new device and make sure you are logged in to iCloud with the same Apple ID as on your old machine. Your notes should then automatically be downloaded on your new Mac. Same for iOS.
Note also that the standard migration assistant of Apple, and restoring a Time Machine backup, should both bring across your Agenda data.