Has a man made satellite or probe ever been flown into the Sun? Either on purpose or by accident?

No. A quirk of orbital mechanics actually makes it take more rocket power to reach the Sun than it does to reach Pluto. There is no way to accidentally go there and it has never been done on purpose. There was a proposal to send an unmanned craft very close to the Sun, with special heat shielding, by using a gravity ist flying of Jupiter to get there, but it was never funded.