The required components are documented in the component impl block. Scroll down in docs.rs until you find impl Component
and they'll show up there.
Apparently there were issues getting required components to show up at the top of the page (from my understanding anyway), so for now they live there.
Not yet. WASM unfortunately does not have DOM access or the ability to call any native JS functions without glue code.
There are packages that work with wasm_bindgen in Rust that can generate that JS for you, but it's all still super early.