There are two cat concerters on that van - were they both changed?
A Catalytic Converter can fail if it becomes clogged or poisoned but there is no way of knowing when it is clogged. Replace your Catalytic Converter when it starts to malfunction.
The answer is yes, it can.
No, if it is clogged it must be replaced.
Yes, it most certainly can if the converter is clogged.
It is not advisable.
Yes it is possible.
Replace it
They can become clogged or they can burn out.
Yes
Yes, you can do serious damage to the engine if the converter is clogged.
Loss of power, and a converter that gets red hot.
It could, yes.