How many watts does an electrical appliance consume?
Q1. Which one should be used to calculate power?
Input or output power

Well, that depends on what you care about. But my guess is how much total power you consume, not how much comes out of your supply, so it's the input.
However, that current is a  peak current of what the supply will draw in a transient situation (plugging it in), so it has nothing to do with power consumption and the approach of simply multiplying the current with the voltage will not take you anywhere.
That's like plugging in a lamp to your outlet, then walking over to your breaker cabinet, see that it's all 10A breakers, and claim that therefore, any lamp you plug into your 220V outlet will consume 2.2 kW. That's not how it works.
Same for the output rating: that's probably maximum continuous power, and there's very few appliances that really have a constant power consumption.
So, the data given on your supply addresses something else than what you care about.
In this situation, the only way forward is actually measuring power consumption in real-world usage. In-line pluggable power meters are &lt; 15€ ...

Q2. Why are there 2 different voltage 100/240V in input section.

Because the same supply can be used with multiple grid voltages.

Q3. What are the difference between input and output in this image?

See Q1.