Federal law requires applicants for CDLs to take physicals and be drug tested.
To get a CDL, you'll have to get a DOT physical done, which will include a drug screen.
Yes
If the vehicle requires a CDL in service, it'll require a CDL for the test drive.
It will.
Yes
yes
You will fail a CDL drug test with ANY detectable amount of THC in your system.
Commercial driver's license can be obtained from the Department of Transportation. All you have to do is appear in their office personally and pass the physical exam, drug test, and the CDL test.
Change "can" to "will" and you're spot on--if you fail they'll pull your CDL.
Most companies will require it, yes.
Yes, they will. And, once you're employed, you'll face random drug screenings, as well.
It can happen, but it will take a very long time.