These are agricultural terms that refer to the death of crops from either too little or too much rain, respectively.
A "locust" is a type of grasshopper that causes destruction by eating crops. The word "caterpillar" refers to an early growth stage of the locust.
This can be stated in active form. AT: "a person, or all your people Israel, prays and makes a request" (See: rc://en/ta/man/translate/figs-activepassive)
The words "prayer" and "request" mean basically the same thing and emphasize that the person is sincere as he makes his request. See how you translated similar words in 1 Kings 8:28. AT: "requests" (See: rc://en/ta/man/translate/figs-doublet)
One possible meanings is that the person's sin is spoken of as if it were a plague. AT: "knowing the sin in his own heart" Another possibility is that the "plague" is a metonym for the sins that the disasters are a punishment for. AT: "knowing in his heart that the plague is the result of his own sin" (See: rc://en/ta/man/translate/figs-metaphor and rc://en/ta/man/translate/figs-metonymy)