Xiaomi Yi Dash Cam - is there a way to lock lets say last minute of video ?

[WhySoSad]

I know there is a "lock" button which protects maybe next 30 seconds of a video, but does it lock also the previous file ?

When I get into some situation which I want recorder and locked, can I just press the lock button and the last lets say 30 second will be saved ?

I just dont get how it works...