CDL requirements are based on the weight ratings of vehicles or combinations of vehicle and trailer. If you attach a trailer rated at 15,000 lbs. to a truck rated at 10,000 lbs, it doesn't require a CDL. If you operate a truck rated at 26,000 lbs., you don't need a CDL. Take that same 15,000 lb. rated trailer off of the 10,000 lb. truck, and put it on the 26,000 lb. rated truck, and you need a Class A CDL to operate that combination.
Anything defined as a CMV will require a CDL, regardless. So if it's pulling a trailer, yes, it will require a CDL.
A CDL license is required to drive a skid loader. Many employers will require a CDL to get positions that require the operation of a skid loader.
You can drive vehicles which require the operator to possess a CDL....
For private use, no state requires a CDL for an RV.
If the vehicle requires a CDL in service, it'll require a CDL for the test drive.
Firefighting and emergency response vehicles are exempt from CDL requirements under federal law. The state may, however, require that a non-CDL Class A or B licence be held by the driver of the vehicle, and individual department policies may require a CDL, rather than a non-CDL licence.
Class 3 truck with a rollback body? No, it doesn't require a CDL.
The presence or absence of air brakes has no impact on whether or not that vehicle requires a CDL.
All classes of CDL require a DOT medical card - A, B, and C. Additionally, anyone operating a commercial vehicle with a GVWR in excess of 10,000 lbs. is required to have one, even if the vehicle doesn't require a CDL.
Vehicles which are not used for on-road use do not require a CDL.
Air brakes have absolutely nothing to do with determining whether or not a vehicle requires a CDL.
No. Just to drive it (if it requires a CDL - not all trucks considered commercial require one).