Which form features a statement of an idea, a contrasting idea, and then a repetition of the first idea?

The direct opposite of strophic form is through-composed form.

Match the following forms with their formal patterns. A-B

Match the following forms with their formal patterns. A-B-A

The opening section sounds marchlike, with accented beats and alternations between instrumental groups. Eventually, a total change of character marks a short, new section. At approximately which time interval from the beginning does this new section appear?