3rd party has nothing to do with your car. it only pays to a 3rd party's claim (e.g. another car, pedestrian, your passenger's bodily injury).
if you want to claim for your car's damage in an accident, you need to have collision whenever your car collide with something, can be a station object, doesn't have to be a car. however, anything not related to collision, such as if it's stolen or got broken into, you need to have comprehensive in order to claim for your loss. but if you hit a deer, some insurance companies would treat it as comprehensive though you actually collided with a deer. kinda weird. don't know why.
from the sentence, looks like it means if your car's actual cash value is less than $10,000, then you cannot buy collision and comprehensive for declared value car. usually, a declared value car is like those antique collectible. the owner declared that its value is $50,000 though the car may just cost $5000 when it was bought 40 years ago. if you want to insure your car, you will need to get your own collision and/or comprehensive lar.