Unfortunately the answer to all of your questions is no. Terragen can be used for game asset creation, but that's not its strongest area. You would be basically limited to exporting heightfields or geometry (OBJ), without textures, and using top-down neutral lighting renders to get any texture export.
Judging by your stated needs, I think you might want to look instead at World Machine, L3DT, or TerreSculptor. World Machine and L3DT in particular are well setup for tiled output, I believe, as well as texture output and other output types.
- Oshyan