Typically, two years. I believe a CDL driver over 55 must update them annually.
To operate ANY vehicle which requires a CDL of ANY class in ALL states (this is federal law - it doesn't vary by state), the driver must have, along with the appropriate class of CDL (A, B, C), a DOT Medical Card. However, this is assuming you're were referring to a Class C CDL - several states issue a non-CDL Class C licence.
You might be able to get the licence, but you won't be able to get the DOT medical card, which will give you a de facto bar from employment as a CDL driver.
If you have a CDL, you're required to have a current and valid medical card, period.
Yes
No.
A medical card is required for the operation of commercial vehicles with a Gross Vehicle Weight Rating of more than 10,000 lbs. If your state requires registration of DOT medical cards, then you must do this if your job involves operating a vehicle for which a medical card must be carried by the driver, even if a CDL is not required.
Yes you do need a CDL to be a medical transporter. Other EMT training is also mandatory.
Anyone with a CDL who self-identified as non-exempt, anyone operating a CMV with a GVW in excess of 10,000 lbs. across state lines, and many states require those operating vehicles which would normally need a CDL, but are operated under an exemption (RVs, farm vehicles, emergency vehicles) to obtain and maintain a DOT medical card.
No, you're not. However, if you're seeking employment again as a commercial driver, you'll be required to have a valid DOT medical card as a prerequisite for employment.
You will not have your CDL revoked, but the moment your medical card expires, you're prohibited from operating a CMV (or any commercial vehicle with a GVWR of more than 10,000 lbs., for that matter) until you get a new medical card. Additionally, you won't be able to renew your CDL without a valid and current medical card.
Typically, two years. Drivers over 55 (IIRC) or who had to be waivered on the physical requirements must update them annually.