1. One-legged gold: One-legged gold is a kind of gorgeous skin, which can be understood as the gorgeous stripes on the tiger.
2. Youth: In nature, tigers are beasts at the top of the food chain. When they are young, they are usually very strong and can hunt large prey. So you can use "youth" to describe the tiger's youth.
3. Folding flowers: When a tiger is hunting, it will quickly "break" the neck of its prey, just like folding flowers.
4. Empty branches without flowers: This metaphor means that tigers have no food (empty branches) if they don't hunt (fold flowers).
So according to the above analysis, the answer of this poem is "tiger".