It sounds like you got a good pistol. Czech armories do a great job of rehabbing their pistols before they sell them off as surplus.
Many modern pistols have rebounding hammers. Think of it as a fourth safety measure, in addition to the inertial firing pin, firing pin block, and the trigger locking safety itself. The rebounding hammer flies forward when fired to strike the firing pin, then bounces back a few millimeters. You can push it forward with your thumb against spring tension, and back it comes again when you ease off.
I've never played with a CZ 82, but the CZ 75 and CZ 97 I've owned both had half-cock positions for the hammer. It wasn't much of a safety feature, but I think it is a feature that has been thought of as a "safety feature" for 250 years on pistols, so manufacturers just design it in. If your pistol doesn't do half cock, don't worry about it too much.
I'll leave your mag release question to someone who owns a CZ 82.
Scott