The Planck length is a trick of math, and it doesn't describe or limit anything.
Remember, length is a subjective property.

If something is the "smallest length," then what happens under GR space contraction?


Back on topic:
Even if electrons were spheres (they're not) with radius one plank length (they're not), the outer surface might as well be infinitely far from the center as far as this discussion is concerned.


It's not 4D spin. It's a quantum property. It's not in any way analogous to anything actually spinning.
It's called that because in the early days of figuring particles out, people noticed that electrons have an intrinsic magnetic moment. They hypothesized that if the electron was a rotating sphere or taurus or anything of charge, that is a current loop, and current loops create magnetic fields. They were wrong. There are serious problems with that model, and plenty of evidence suggests it's not good. Still, the name stuck. Spin.

It's really no worse than calling quarks by color words. Color doesn't exist on that scale. Color is something that is produced by charged particles changing states. I.e. photons are emitted when charged particles change states. An electron could change states to produce a photon of any color, so the notion that a particle has a color is just another one of those things in QM where your expectations have to take a back seat.