Answer to Question 1
After the first verse, Magic Sam follows the usual three-line (AAB) stanzas, but they are much longer than the expected twelve-bar length. For example, the second stanza starts on the word love, (Yes I) love you . . . and lasts for twenty-seven measures at a fast tempo.
0:05stanza one
0:30stanza two
1:19stanza three (repeat of stanza one but as a 3-line stanza)
1:43guitar solo
2:19repeat of 3-line stanza one
Improvised repeated lines and end
Answer to Question 2
A riff or repeating melodic-rhythmic idea that continues throughout the entire selection