Solid bounded by given region.

Questions
1

Why can’t Wolfram do this: plot solid bounded by (z=0, z=4(?(X^2+y^2)), and (?(X^2+y^2))=2) ? Am I missing an app or widget somewhere? Please and thanks!

2

I am not quite sure I understand your constraints, but probably you want to use RegionPlot3D. Here is an example which may be close to yours:

RegionPlot3D[
 z > 0 && z < 4 Sqrt[x^2 + y^2] && z > 2 Sqrt[x^2 + y^2], {x, -10, 
  10}, {y, -10, 10}, {z, 0, 20}]

Also ContourPlot3D can give some insight:

ContourPlot3D[{z == 0, z == 4 Sqrt[x^2 + y^2], 
  2 == Sqrt[x^2 + y^2]}, {x, -10, 10}, {y, -10, 10}, {z, 0, 20}]
3

Am I missing an app or widget somewhere?

No, what you’re missing is called syntax, not widget

RegionPlot3D[0 <= z >= 4 Sqrt[x^2 + y^2] && (x^2 + y^2) <= 4, 
{x, -2.1, 2.1}, {y, -2.1, 2.1}, {z, -.1, 8.1}, PlotPoints -> 35, 
 PlotRange -> All, PlotStyle -> Directive[Yellow, Opacity[0.8]], 
 PerformanceGoal -> "Quality"]