Performing “The Star Spangled Banner”- when did it become common for the last lines to be played at a much slower cadence? What about very stylized performances?

I have several questions about the history of how the song “The Star Spangled Banner” (since 1931, the official national anthem of the United States) is performed:

• the last two lines “O’er the land of the free / and the home of the brave” are typically performed at a much slower cadence than the rest of the song. How long has this been the practice?

• the audience typically starts to cheer and applaud the performer at the end of the second to last line (the high note in “… of the free”) rather than waiting until the completion of the song. How long has this been the practice?

• Many performances of the song -- especially vocal performances -- seem to apply pretty dramatic variations to the original score: vocal gospel-music-style flourishes, and sometimes even dramatic changes to the melody or emphasis on creative harmonies. Given how protective Americans tend to be about other national symbols such as the flag, it is perhaps surprising that Americans not only tolerate but seem to encourage these kinds of liberties to be taken with the performance of the country’s national anthem. (There are of course exceptions that are regarded as crossing the line into inappropriateness — Roseanne Barr’s 1990 performance comes to mind). In general, then, for how long has this practice of taking stylistic liberties with the performance of “The Star Spangled Banner” been around?