Gustav Mahler would be my answer. Strauss was also composing during the late 19th and early 20th but Mahler created more of a fusion between the two.
6.
You can tell what key it is in by the starting note. Therefore, for example the first question is on "D", and it had a flat accidental. Therefore it is a Db (D flat). Now, we can use the circle of fifths
[first attachment]
to help find out where the sharps and flats fall, and since this is a major scale, the pattern is Wholestep Wholestep Halfstep Wholestep Wholestep Wholestep Halfstep (WWHWWWH).
Therefore the pattern is Dflat Eflat F Gflat Aflat Bflat C and Dflat again. You can write there as notes on the scale
[second attachment]
You can do this for the rest of question 6.
∆∆∆
7.
Just choose a key signature from the circle of fifths (an easy one is G) and put that key signature on your staff. Secondly, choose a time signature. The easiest is 4/4. If you're in "G", start in key of "G" and make a simple tune. e.g
[third attachment, scroll right]
for the other tunes, just choose different time signatures and key signatures and switch up the tune.
Hope I helped and good luck!
I'm like, way too obsessed with the 2000s and shouldn't know as much as I do. So, like, excuse me if I go a bit overboard here.
Fashion in the early 2000s was mainly form-fitting on the top (blouses were pretty big), while the bottom was more loose, like flared jeans or sagging your pants. Loose, trapeze type dresses (but like, structured on the top but completely unstructured past the bust. I don't think there's a name for that type of dress, it's just so weird and /such/ a fashion crime).
This started to change around maybe 2004-2005? ish when emo/pop punk started getting way more traction and Paris Hilton became a major style influence (like, I could write an essay about her genius. She influenced an entire dam/n generation and CREATED the Kardashians. What an icon). Jeans became tighter (if emo did anything right, it was getting rid of bell bottoms for good) and more low rise. Actually, severely low-rise (thanks, Paris Hilton). And the god awful whatever-the-heII-that-was dress was replaced by slip dresses (courtesy of our lord and savior, Paris Hilton again). Oh yeah, I also can't not mention the Juicy Couture tracksuits which were /huge/ in the early 2000s. (Also, I think tube tops were either early 2000s or mid-2000s, which was major because the partying scene literally exploded.)
TL;DR mostly form-fitting. If you need examples, just cite Paris Hilton or Juicy Couture.