Toilets, Sinks, Showers, Tubs and Disposals - Asking too much of a wax ring?

Question:
Should the toilet's wax ring be able to prevent a leak when the clog is in the drain down below the floor and the water backs up through the pipe and fills the toilet bowl?

Details:
I had a clogged toilet on the first floor. After vigorous plunging, the wax ring failed and water leaked out from under the toilet. So I pulled the toilet, and with a garden hose determined the clog is down in the soil pipe. (Cast iron pipes, circa 1960).

So I replaced the toilet with the new wax ring, but before clearing the drain pipe's clog (using a cleanout in the basement), I flushed the toilet. The first two flushes were fine, but the third flush flooded from under the toilet again, and also down around the outside of the pipes in the basement. The standing water in the bowl continued flooding on the bathroom floor until the bowl was empty.

So is preventing a flood under those circumstances (the drain is clogged and filled with water) beyond the capacity of what the wax ring is designed to do?

Thanks.

The wax ring should have been able to hancle the clogged line. That it didn't tells me that the original ring was old and about to fail.

When the new ring failed on the 3rd flush (while the line was still clooged??) means you probably needed to use a larger ring -- a #3 or even a #10. Your flange is below the level of the flooring that the toilet sits on.

Thanks for the prompt reply lefty. Since you told me it should not have leaked, I pulled the toilet again, and now realize that the cast iron flange's inside diameter is about the same size as the outside of the wax ring (about 5 in).
So the new wax ring was actually pushed partway down into the flange. Does this mean I really need two wax rings? One ring that goes inside the flange, and is pushed down so it sits on top of the end of the pipe itself, and makes the wax even with the top of the flange, and a second ring above that? (BTW, you stated that the flange is below the level of the floor, it is actually about 1/2 in above the floor.)

Thanks again.