"Beth" is the name of the second letter in the Hebrew alphabet. Each of verses 9 through 16 begins with this Hebrew letter. See "Formatting in this chapter" in [Psalm 119 General Notes](../119/intro.md).
This question is used to introduce a new value to the word of God. This rhetorical question can be translated as a statement. Alternate translation: "This is how a young person can keep his path pure" (See: [[rc://en/ta/man/translate/figs-rquestion]])