When administering first aid to a crash victim with an open compound limb fracture where bone fragments protrude through the skin (开放性骨折), what is the critical medical rule?

1. Do NOT push the protruding bone ends back into the wound (to prevent deep bacterial infection); cover with sterile dressings and immobilize the limb with splints bridging adjacent joints
2. Push the protruding dirty bone fragments back deep into the tissue with bare fingers
3. Wash the bone ends with hot engine coolant to disinfect them
4. Bend the broken limb repeatedly to check if the marrow is leaking