Can you shoot retreating soldiers?
Can you shoot retreating soldiers? No it's not a war crime. Fleeing enemies are not surrendering enemies. Fleeing enemies are simply enemies that are retreating back to regroup and fight and kill you another day.
Are you allowed to play dead in war?
Playing dead to escape an enemy is okay. It would be considered a ruse of warfare, albeit a very dangerous one. Still, it could be and has been used by soldiers with little other choice. However, playing dead and then turning on an enemy that passed you by, might well be considered a violation of the rules of war.
Can you shoot medics in war?
According to the Geneva Convention, knowingly firing at a medic wearing clear insignia is a war crime. In modern times, most combat medics carry a personal weapon, to be used to protect themselves and the wounded or sick in their care. By convention this is limited to small arms (including rifles).