Yes
The same as it would be otherwise, minus the air brakes written test.
If you already have a CDL, you take the written air brakes test, then do a road test in a vehicle of the appropriate class which is equipped with air brakes.
Yes - both a written and road test are necessary for the P (passenger) endorsement, regardless of what class of licence you currently possess.
You have to take the written test, and take a road test in the appropriate class of passenger vehicle. If you have a Class B CDL, but your road test is in a vehicle requiring only a Class C CDL, then your endorsement will come with a restriction limiting you to Class C passenger vehicles. If you're trying to get endorsed for a school bus, a criminal background check is also required. The DMV can tell you how to go about doing this.
You would have to be more specific about what a Q restriction is. Restriction codes vary by state (here in North Carolina, they are numbered). However, to test for a passenger endorsement, a road test is required as well as a written test, even if you have a CDL already.
Yes, it would be for either S or P endorsement.
Take the written air brakes test, and perform a road test in a combination requiring a Class A CDL which is equipped with air brakes.
Depends on what class of CDL you're going for, among other things.
When you got your CDL did you take the road test in a air brake equipped vehicle? If you did not then you have to retest to add air brakes. Not the whole test just the air brake portion both written and pre-trip portion of road test.
They're all in the CDL handbook. Study it, learn it. If you're not competent enough to do that, you have no business holding a CDL.
The class of the Commercial Drivers License , A, B or C refers to the weight of the vehicle. When a person gets a CDL, they take the General Knowledge test.
Take and pass the written passenger test, and do a road test in a passenger vehicle. If you take your road test in a bus under 26,000 GVWR, you'll be restricted to passenger vehicles requiring a Class C CDL. If you take your road test in a single vehicle over 26,000 GVWR, you'll be restricted to operating passenger vehicles requiring a Class B or Class C CDL. You're really not going to find any Class A CDL passenger vehicles.