“Raw” RR intervals are the RR intervals that are received directly from the HR monitor and have not been cleaned or corrected for artifacts such as ectopic beats or signal noise.
“Corrected” RR intervals are the RR intervals after our algorithms have of detected and corrected artifacts such as ectopic beats or signal noise to provide a more valid signal for HRV analysis.
The answer to this varies based on your hardware (and has almost nothing to do with the app). That being said, the Elite HRV app is designed to remain connected as long as you are within signal range (even if some heart beats are dropped due to distance).
Research standardized calculations such as RMSSD can still appear slightly different between systems. This could be due to differences in hardware (heart rate monitors, etc.). But it is usually due to differences in the way misreads and signal noise are handled.