If I'm doing manual printing on the DR, is the data printed out at the moment it is triggered (including for key operation)?

The current data is not necessarily printed when the manual printout is started. With data that is manually printed, 1 scan's worth of data is held every scan. When a manual printout is requested, that 1 scan's worth of data is sent, and printed out. Therefore, if a manual printout is requested during a scan, it's the previous scan's data that gets printed out.