Where: The photo was taken along Gap Road, now the eastern end of Queen's Road East. The identifying landmark is the building in the background:
That was the Royal Naval Hospital, near where the Ruttonjee Hospital is today.
When: The road got its original name, Gap Road, from the cutting it passed through between Wanchai and Happy Valley. Here the right (north) side of the cutting has gone - there's just a piece of rough, flat land in its place. That used to be Morrison Hill, but it was dug away in the 1920s, and used to reclaim land off Wanchai.
I'll guess this was taken soon after the reclamation, around 1930.
Who: A large group of soldiers:
Can you see any clues in their uniforms that tell us more about these men?
What: The black armbands indicate this is a funeral procession, heading to one of the cemeteries in Happy Valley.