Ad 1) there’s nothing magical about it just a more or less random value that gave an exaggerated effect. So in stead of using two Divide Nodes, you can use one with a different value.
Ad 2) i don’t think there is a better way to make this example….
Ad 3) in 2.93 there is a Spreadsheet:

And I used Ceiling in my example, because the Primitive Icosphere in 2.93 doesn’t have a zero Subdivisions (at least, it is the same as 1 Subdivision):
