Can I charge my tablet with a plug that has different output voltage and current? Can I charge my tablet with a plug that is for an old fashioned mobile phone? The plug has a different output voltage and output current.
What are the output specs of the charger?

With a different amperage, there's no risk unless the amperage is very high. A different voltage might cause problems. Modern devices need 5V and anywhere between 500mA to 2A. Don't try something like 9V. Also, using high amperage to charge is not good for long term health of the battery.