Z-ordering is indeed not perfect, and (while the problem seen in that image is very uncommon) it won't be able to draw intersecting polygons correctly. If you want to draw it correctly, you'd need Z-buffering, which needs a lot of RAM. And unfortunately, the 83+/84+ hasn't got much ram.

EDIT: 

so, GUpdateBuffer(id) transforms all the vertices? That seems like a quite simple syntax, but when the amount of vertices changes, do we have to generate a new buffer every time? Because that sounds kinda slow

indeed, I didn't think about this. So something like :

GBufferUpdate(id, start_update,end_update)

with start_update the first vertex to update, to end_update ?

yep, you can generate up to 255 VBO, and choice wich one to activate with id . You can also delete them - but this only free memory ; meaning that even if you have suppress some VBO ; you will not be able to generate other if in total you have generated 255 VBO. Hope you will understand me  

exactly that  cause handling remplacement woud be a way to much difficult (and heavy).

using custom camera, yes. Basically , you create a new camera ; rotate point around this camera , go back to the classic camera , and render point.
For example ; if I want rotate point 10,10,10 around X,Y,Z, with angle A B and have a world camera, I could do something like that :

GNewCam(°GWORLDVIEW)

While 1

GNewCam(Data(Ar,Br,Xr,Yr,Zr,0r))

GRotate(10,10,10)
GDelCam()

GVertex({°GVertex}r,{°GVertex+2}r,{°GVertex+4}r)
Pxl-on(,{°Gvertex+2}r)

GGetkey()

DispgraphClrdraw
EndIf getkey(15)

however ; in the next version of GCORE , the format of the camera will slighty change (nothing big) ; that why I still doesn't made a tuto about it.
The engine in itself can handle 2 different camera.

EDIT this code work for the "old" version though

After some test, seem that VBO is almost as fast as "classic" code. So I will keep that  . I have to try with dot point, though cause acessing it will be more slow


EDIT : ok so it seem that with dot , VBO run at 53-54fps (classic cube) ; and without it run between 55-56 fps (without any super secret settings :p). However, I didn't optimize *yet* the VBO's code