Which of the following statements about protecting children and others is INCORRECT?

1. ①A guardian of an infant (under 6) must not let the child walk alone on a road with heavy traffic
2. ②A guardian must make a child wear protective gear when the child rides a bicycle on the road
3. ③If the guardian accompanies the child, the child may ride a personal mobility device on the road
4. ④A police officer who finds an elderly person (65 or older) having difficulty walking on a crosswalk must take appropriate measures for that person's safety