Using a GoPro as a Dashcam: Benefits and Drawbacks

Yes for occasional recording with a secure mount and power, but heat, storage, incoming calls and manual operation make it less dependable than a dedicated camera.

Some GoPro settings and models support looping capture, but confirm the behaviour for your exact camera. It may not provide the same automatic file protection as a dash cam.

Do not assume it will. Startup and recording behaviour depend on the model, power setup and settings, so a manual start may still be required.

That is unwise. GoPro documents temperature-related shutdown behaviour, and a visible camera left in a hot vehicle also creates security and battery concerns.