Woah!! This is greatly detailed, and a great guide for people who can't draw hands!! ^^
(I too can draw hands but mostly irl, and NOT on digital drawings:3 oopsies lol maybe it's my phone size or Idk I find it difficult to draw without a pencil/pen lolol)

Don't ask for toes, I do not know how to draw toes. Ankles can do.

add muscle accordingly, since fatter hands lose the "tendons" part of hands + fingers will look larger

no shame in using references

you can still use a pentagon shape but, why make it harder for yourself when it looks like a triangle. when you break down the basic shape of a hand it's easier to add flesh and tendons from there

oh and in certain angles (say thumb + index) replace pentagon shape with a triangle instead, since the backside of the palm is obsolete usually