Hi,
im new to ZBrush. I have the zbrush 4 version and got some lynda.com tutorials from a friend. When I make a new sphere3D i cant lower the sdivs, even I didn’t see Geometry HD etc… When I load some pre-made work from the exercise folder. I can increase/decrease the sdivs and see all the tool menus like Geometry HD etc… What I need to do to have all the features in the palette?
Thnx
tool>makepolymesh3d
You should watch the getting started tutorials in the zclassroom.
Everything you’ll need to know for the basics of Zbrush is included in that section. Including the problem you’re having right now. 
What you’re trying to do is sculpt/divide a mathematically generated mesh. These 3d starter meshes have tool>initialize that no other mesh will have. This palette will let you change things like the size, scale, number of segments, the curves of certain aspects of the mesh, etc. This can be very useful for starting off meshes. But you need to inform zBrush that you want it to become a sculpting mesh once you’ve set up everything, which is why you hit “makepolymesh3D”
I hope this helps.