Yes. If your DOT expires, then the first thing which happens is your CDL is downgraded, and you can no longer operate a vehicle requiring a CDL. From that point, you have a certain time limit to a: get an 'exempt' self-declaration classification (which allows you to circumvent downgrading your CDL, but does not permit you to operate a CMV requiring a CDL) b: downgrade your CDL, or C; renew your DOT medical card and register it with your state's DMV or equivalent. If none of these are done within the alloted time period (typically, 30 days from notice being sent), then your license will be completely suspended until the situation is rectified.
Yes
If the commercial vehicle requires a CDL to drive it, you do.
If it requires a CDL, then yes - that's federal law.
10,000 lbs. GVWR and up in a commercial use vehicle, and the answer is yes.
You're required to have a current medical card on your person at all time when you're driving a vehicle which requires a CDL. In any state. That's federal law.
If you have a CDL, you're required to have a current and valid medical card, period.
Even if you were able to get the licence, you would never get a DOT medical card, which is required for employment as a CDL driver.
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.
No.
Yes
You would need to get a medical waiver in order to do this.
You must have a current DOT medical card to maintain an active CDL in EVERY state. That is a federal law.
Typically, two years. I believe a CDL driver over 55 must update them annually.