Unwrapped bread will dry out and thereby go moldy more slowly than wrapped bread. But it will grow mold.
If you ate it you would have construpation and you will fart because of the acid created by the mould
If you keep your bread in the refirigerator that usually keeps the moulding postponed for up to 2 weeks. If you don't like your sandwich at room temperature then you could leave the bread out for a...
It's all the air going away so it starts to get moldy.