Pass-tense is a misunderstanding of the term past-tense.
gave
the answer is: Had
No, "become" is not in the past tense. The past tense of "become" is "became."
No, not all past tense verbs are compound words. Past tense verbs are formed by adding -ed, -d, or -t to the base form of the verb in regular verbs. Compound words are formed by combining two or more separate words to create a new word with a distinct meaning.