1. You must have your permit(s) at all times. There's no getting around that one. 2. If you own the semi truck, and you have deemed it your home, then no, you do not have to have a DOT physical card. 3. If you work for a company, and you are driving one of their semi trucks, then you must have a DOT physical card, by law.
If you get pulled over, the officer is going to ask for your license, your DOT card, and your permits. I hope this helps.
That is actually dependent on which class of commercial driver's license you hold. If you have a class 1 commercial driver's license, you can drive a semi trailer. With this license, you can also drive all other motor vehicles or vehicle combinations, but you can't ride a motorcycle. You must also have a DOT physical examination report.