
Just spend that time learning blender instead.

So in essence, none of the above if you're serious about learning unless you're ready to drop full hours in zbrush proper.

And even then use it anyway, it's the future and in gamedev or anything else really will be one of the most widely used supported apps out there. If you want to learn sculpting just use Blender honestly unless you're ready to buy a monthly sub to zbrush proper. Sculptris is a voxel modeller/sculpting tool which gets you familiar with some ideas behind that, but it's less powerful than even blender sculpting these days.

Coremini is a very limited feature version of Core which is a very feature limited version of Zbrush.
