Resetting the charge cycles is definitely one of the steps when refurbishing batteries (putting in new LiPo cells)... unfortunately I'm not an expert in the procedure, but it can possibly be done with a cp2112 and the DJI battery killer app, all...
A sophisticated fraudulent seller will have access to the needed equipment to reset the charge cycles... this alone isn't a reliable sign of a good battery I'm afraid.
The most reliable before the buy is instead the seller credibility & return...
In general, DJI photo drones doesn't draw amps to the same degree as FPV Acro quads... but full stick commands will cause voltage drops even on photo drone batteries & it's worse if both the elevator & the throttle is maxed out at the same time...
If activating "Use online elevations" in the settings & marking the checkbox "Above ground" on each waypoint... the set height for each waypoint will be above ground right below the waypoint & not relative the takeoff point.
This works ok, but...