Since you're not familiar with the Contender/G2, the easiest way to tell the difference is to pull the hammer back to cock it. Put your thumb on the hammer, pull the trigger, slowly thumb the hammer to the frame. Then try to recock the hammer. The G2 will cock again, the Contender won't until you break open the barrel.
To remove the barrel, take the fore-end off, open the barrel, push out the barrel pin.