1. You can get the model of the sprocket here:
Inventor 2009
STEP (you have to right click and do save as in some browsers)
2. Yes, thats how they are used in the kit chassis
3. You really dont need to model the individual links but if you must I would use an insert constraint to make the links into a strand and then use the concentric constraint around each tooth on the sprocket as well as a flush so that the links line up with the edge of the sprocket.