Yes! Then you would have triple exhaust.
I doubt a holed exhaust will pass. Apart from an increase in engine noise, as the exhaust is not working properly, exhaust fumes could seep into the interior of the vehicle - affecting badly anyone inside the vehicle.
To repair a hole in a Borla exhaust try taking vehicle to a reputable muffler shop. Popular opinion states that having the hole welded will work but make sure the after market repairs are legal in your state.
no
Depends on where the hole is. Before an oxygen sensor, it may be causing your vehicle to over/under fuel itself, and in that case possibly. Close to the manifold, it may allow much cooler air to the exhaust valves and warp a valve and then the answer would be yes. Further down, say at or beyond the catalytic converter, typically the answer would be no.
Radiators do not have exhaust.
The exhaust gets into the passenger compartment usually by a hole in the body of the vehicle. Another possibility is if there is an exhaust leak at or around the engine compartment,if this is so the ventilation for the passenger compartment can pull in the exhaust. Also you should check that the end of the tail pipe should stick out a little past the bumper.
You can drill a hole in anything as long as you have a strong enough drill bit and drill. But why would you want to drill holes in your exhaust? The exhaust piping is there to route exhaust gases away from underneath the car so they don't pool up underneath your car and seep into the cabin and cause a variety of health problems.
If the hole is smaller than a nickel, I would not worry about it. If the hole is on the bottom side of the exhaust pipe, it might actually be a good thing, as it would allow the water in the exhaust to drain out before it enters the muffler. Some newer cars have drain holes in the exhuast system to prevent things from rusting out quickly.
One of the causes could be a hole in the exhaust
there should not be any drain holes in an exhaust
Exhaust gasses are escaping through a hole or rotted section of exhaust system