Not necessarily, but specifics matter in regard to this question.
Depends on the GVW of the trailer and the Gross Combined Weight Rating of the truck and trailer.
No, you don't. RVs are exempted from CDL requirements. Your state, however, may require that you upgrade your licence if the vehicle is over 26,000 lbs. GVWR.
GVWR of the trailer, GCWR of the combination of the two vehicles, and usage matter. We'd need to know this in order to ensure an accurate answer to this question.
For private, recreational use, no. And this applies to all states.
If the Gross Combined Weight Rating of the truck and trailer is in excess of 26,000 lbs, yes.
So long as the Gross Combination Weight Rating of the two vehicles is less than 26,001 lbs., then no.
No you do not need a CDL for this. You will need to have a license plate and registration for the trailer along with opperating tail and brake lights.
So long as the total Gross Combination Weight Rating of the vehicle is 26,000 lbs. or less, and the weight actually remains under 26,000 lbs., then no, you don't. You also don't need a CDL if it's a vehicle exempt from FMCSA regulation, such as a recreational vehicle.
Anything defined as a CMV will require a CDL, regardless. So if it's pulling a trailer, yes, it will require a CDL.
Depends on the GVWR of the trailer, the GCWR of the entire combination, and its use.
If it's a commercial use vehicle and the Gross Vehicle Weight Rating of the tow vehicle and of the trailer combine to make a Gross Combination Weight Rating in excess of 26,000 lbs., then yes, a CDL is required.
If the total weight rating of the combination is over 26,000 lbs., then yes, you will. If the trailer itself is rated at over 10,000 lbs., you will need a Class A CDL. If it is rated at under 10,000 lbs., then you would need a Class B CDL. Note that this only applies to combinations over 26,000 lbs. GVWR - you can pull a 15,000 lb. rated trailer behind a 10,000 lb. rated truck with a regular Class C licence, but, if you pulled that same trailer behind a 15,000 (or more) rated truck, you'd be operating a combination rated over CDL weight, and would require a Class A CDL.