If the vehicle's Gross Vehicle Weight Rating is in excess of 26,000 lbs., yes.
The length from the middle of the steer wheels to the center point between the drive tandems (for a tandem truck) or center of the single drive axle (on a single axle truck).
There's no such thing as a one axle truck. There has to be a minimum of two axles. "Single axle" if a term referring to a truck with only a single drive axle, and doesn't count the steer axle. Same with "tandem axle", "tri axle", "quad axle", and "quint axle".
The power unit has a steer axle, and only one drive axle.
Those designations actually exclude the steer axle, and only count axles behind the steer axle, so what you're talking about would actually be a truck with two axles - a steer axle, and a single drive axle.
20,000 on the steer axle, 34,000 on the drive tandems together.
A tandem truck usually refers to the amount of axles on the trailer or tractor. A single drive axle on a tractor would be referred to as a single, or the same for one axle on the trailer. I have seen it referred to the amount of tires on the end of an axle. When there are two tires on the end of the axle, that would be referred to as a dual, not a tandem.
The exact same thing as the first drive axle.
#1 axle is the steer axle, #2 axle is the front drive axle, #3 axle is the rear drive axle.
Gross 52,000 lbs
What type of truck and trailer? For all I know, you could be talking about a Ford F650 and a single axle utility trailer. If you're referring to Class 8 vehicles, something like a single axle tractor towing a single axle trailer would be allowed an interstate GVW of 52,000 lbs.
Not if it has a Gross Vehicle Weight Rating of 26,000 lbs. or less.
From the center of steer axle to center of rear axle on trailer. If you want just the truck it's the center of steer axle to center of rear drive axle.