By the RASPBERRY PI 2 MODEL B specs: http://en.wikipedia.org/wiki/Raspberry_Pi
The power rate of it is 800 mA, what are the possible effects if the charger output is lower or higher than 800 mA?
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You are likely to have issues with that power supply, 700ma was the minimum required by the original Pi. As you state 800ma is the minimum requirement for model 2 Pi's. Under current can manifest in many ways including SD card corruption, system instability, WiFi connection issues etc.
As for using a charger that supplies greater than 800ma you can use any charger up to 2000ma without problems.
One extra note: don't rely on the label on the charger, many problems have been traced to chargers not delivering the current they advertised.