Loss of power, poor fuel mileage, hard starting, and the converter will get red hot. Normally the check engine light will also come on.
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.
Replace it
Yes it is possible.
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.