1. Use
dbObjectExist() to check if an object was created successfully (returns 1 if object exists).
2.
dbLoadObject() loads an entire object with all its animation data,
dbLoadMesh() just loads the mesh (vertices, polygons). You can use meshes to change vertex positions etc.
3. Limbs are what most other programs/engines call bones. For example if you would like to position a sword at a players hand, you could position the sword object at the position of the players hand limb.
4. Don't know about Blitz3D commands, but in DarkGDK there is no such things as parent objects (unless you create your own object data structure).
Now the plot thickens, the fps decreases, and the awesomeness goes through the roof.