If you need $6 to pay for parking, and the largest commonly available coin is a quarter, that means you need 24 coins to pay. If the value of currency was such that the parking only costed $3, or if dollar coins were more common, you'd need less coins to pay.

It's required to do any intialization, particularly for compound futures (e.g. a "join" or "select" type of combinator), since you need to be able to move the future from where it's created to where it's eventually used/polled. I assume some of those cases could be subsumed by &uninit if that existed yeah.

For 3, some objects only need to be pinned under certain circumstances, e.g. futures only need to be pinned after they're polled for the first time, but not before. So it's convenient to separate the pinnability property to allow them to be moved freely beforehand.

I don't quite understand the usecase you have in mind for 4.

This is also something that Rust does protect against in safe code, by requiring initialization of all memory before use, or using MaybeUninit for buffers that aren't, where reading the buffer or asserting that it has been initialized is an unsafe operation.

    #![feature(closure_lifetime_binder)]
    fn main() {
        let identity = for<'a> |x: &'a i32| -> &'a i32 { x };
    }

I don't know the specifics of the OoTR algorithm but in general they work by considering a set of items which are currently "available", and then progressively picking a random item to place only in locations which are reachable with that current set of available items (which is expanded with each placement).