I would like to know, is it possible, that I draw line or circle with specific lenght/radius (instead of I move the mosue and change the lenght), like type xx mm and I get a xx mm lenght line or circle.
And how can I measure angle between this lines?
You can create sphere or line using VTK source objects (vtkSphereSource, vtkLineSource, etc.) and set their output in a model node as input. See for example here and in PerkLab Slicer programming tutorial.
You can compute angles using trigonometry functions (e.g., arctan2 between line direction vectors). See a complete example here.