LOD models also work on commercial edition, you just have to name your models like this: enemy_0.mdl, enemy_1.mdl, enemy_2.mdl, were _0 is the main model and _1 and _2 are the lod models.

Mipmaps are handled automatically by the engine when you use mipmapped textures, you can choose how its done through d3d_mipmapping http://www.conitec.net/beta/ad3d_mipmapping.htm

3D Gamestudio A8 Pro
AMD FX 8350 4.00 Ghz
Gigabyte GeForce GTX 960 4GB