I don't know if there's a tag for the five impossible requests but the five items here are them (from touhou wiki):
"The first was to bring her the stone begging bowl of the Buddha from India. The second was to retrieve a jeweled branch from the island of Mount Hourai. The third was to seek the legendary robe of the fire-rat of China. The fourth was to retrieve a colored jewel from a dragon's neck. The final task was to find the legendary Cowry treasure of the swallows."