Q: "A young woman walking on the sidewalk." Does this mean that "a woman is outside"?
A: yes

Q: "A person with a brush looking at a large rock." Does this mean that "A person is getting ready to paint a rock."?
A: it is not possible to tell

Q: "People auditioning on a stage dancing." Does this mean that "The people are wearing ballet costumes."?
A: it is not possible to tell

Q: "Three young girls walk down a sidewalk." Does this mean that "Some people strolling along"?
A:
yes