Ha! In my day, you could get “dropped” (a symbol, usually the frat letters, on a chain; if no frat, then the guy’s initials). It was considered not quite as serious as getting pinned (his fraternity pin–or whatever pin he could scare up) which led directly to engagement, but about on a par with, if not exactly like, getting lavaliered. The lavalier people seemed to be from further south.
As to the knees: they were rouged to stand out.
My mother rolled her stockings from the 1920s until the 1970s, when she started wearing those knee-high things. She had a permanent crease just below her knee from doing it. However, she gave up putting blush on her knees (as we would say today) when she gave up short skirts–which was probably 1929.
It was done to make the knees look more dimpled. Exposed knees were very new in those days.