Your full flight track is in the flight log. Once imported into a program with a DEM, such as Google Earth - that will show height AGL. Alternatively, if you post photos or video, height AGL can be seen in the EXIF data or simply estimated from the field of view of the camera. So it would be unwise to assume that the FAA or other LE authorities would be unable to verify whether you broke the law.
Question 1 :
Flight track log will show DJI Go / Go4 results for height. Would that not be faulty data as the AC passes over uneven terrain ? It has no Geodetic correctors.
Question 2 : There have been a number of posts here and on DJI forum about large errors in the EXIF data in recordings taken by DJI gear, have you had better results ?
Here's one example thread ..
Altitude information on EXIF
another .... (I know its headache stuff !!)
Wrong altitude data from drone location coordinates