Re your first question, first let's define cold. DJI apparently defines it at 15 C (59 F) which you might not think is cold but your battery regards 15 C as cold. Yes, it's risky flying with cold batteries but it's especially risky in cold weather. The risk is you might unexpectedly get a sudden voltage drop in one of the cells causing a sudden and unexpected critical battery auto-land or even a drop from the sky. The good thing is your battery will warm up while it's discharging, so if you're in a moderate air temp with a fully charged battery it's not as important. But in cold weather, you want to be sure your battery is at least above 15 C and you'd want 20 C (68 F) to be safe if you're flying in cold weather. Hope this helps.
