Answer:
Option 2 and option 4.
Explanation:
In option 2, the phrase "like a waterfall" is a simile. The word "like" followed by the comparison of something exaggerated is usually a giveaway to determine a simile.
In option 4, the phrase "Herculean task" can be classified as either an idiom or an allusion (or both). An idiom is an exaggeration of something and an allusion is when a phrase relates something to a work of literature. In this case, it's relating to the story of Hercules.