cracking exhaust valves

[dumb person]

i found some 2 strokes would not run without an exhaust while others would. Also heard that without an exhaust or backpressure that the piston rings would break eventually, maybe from having no downward pressure on the exhaust side while still having pressure on the other side caused them to shift in the piston lands? A motorbike mechanic told me it would break them but i never tried it myself.