1. Some elements of the stills that tell us that '10 Things I Hate About You' is a teen movie are:
Kat and Pat staring at each other angry confrontations between two (moody) teens
Ms Perky - disapproving or disappointed adults, most likely teachers and parents
Cameron and Bianca together young love'
Teenagers are predominant in all stills
Grungy rock bands and emphasis on music rebellion and hobbies
The prom stereotypical of films involving teens and high school
Fights both between friends, siblings and people of the opposite sex
Top left We know that the setting is the high school prom, after watching the movie. There are bright lights and other people (probably dancing look at the limbs in the picture) in the background.
Middle left This still's setting is also the prom. There are bright disco lights at the back (where the rock band is). Apart from the rock band on the stage, there are other teens (who most are dressed up formally) in the background. They are dancing in couples and with friends and generally just enjoying themselves.
Bottom left This still is set either on the balcony or in a sun room. There are large white columns (that hold up the ceiling, roof etc.), and you can see the garden. It seems to be quite a messy garden, but we can't be sure, as the background isn't in sharp focus. There are also potted plants.
Right This still is obviously set in a school hall or office. This is obvious as there are quite dull and boring colours that most schools incorporate into their buildings and the lockers (or cupboards if this was in an office of the principal, student counselor etc.). There are a few windows and potted plants. You can also see a few items (probably personal items) on the top of the lockers/cupboards.
Serious (between Pat and Kat in their confrontation, kind of serious in the conversation between Kat, Cameron and Bianca and quite a serious scene between