andrew...your questions are valid, your flight instructor should be able to answer them, and if he can't...ask him to look it up and get back to you.
there are all sorts of ways to fly a plane using a different combination of controls. There is a story, true, of a Delta Airlines Lockheed 1011 Tristar that took off out of San Diego, USA...its stabilator jammed...the pilots figured it out and used assymetric thrust, flaps, and other ideas to keep the plane under control (they couldn't get the NOSE to come down in the normal way)...they managed a safe landing at KLAX.
IF you make a normal turn in the C172 and the ailerons jammed, you would have a decent chance of stopping the turn with the rudder. But you would have to watch your airspeed as there will be much more drag slowing you down.
I encourage you to read many books about the subjecte of flying...including the following"
The Spirit of St. Louis
Fate is the Hunter
Stick and Rudder
and see if you can't find a better instructor