If a timing chain on a 2003 Camry comes off or breaks will it do engine damage on a 4-cylinder?
NO, the 2003 Camry 4 cylinder in NOT and interference engine. If the chain breaks you will just be stranded. A chain breaking is a very rare occurrence. You will hear noise and usually the engine will perform poorly long before the chain breaks. But as with any engine, it is possible for it to just break suddenly.
Generally if the timing belt breaks, it will not do damage apart from the cam, etc. being out of time. However, if the belt streches thru wear and slips on timing, this can do serious damage, such as beding rods and valves. Sometimes in this case if you are really lucky you can have a rod go through a piston, then you need a major rebuild.