Re: "longest chain", the first release of Bitcoin actually used longest chain rather than most work! This was secretly changed by Satoshi very early on, presuma

Re: "longest chain", the first release of Bitcoin actually used longest chain rather than most work! This was secretly changed by Satoshi very early on, presumably when Satoshi realized that "longest chain" is broken and "most work" is the correct protocol. This would have been a hard-fork if not for the fact that at the time hashpower was so low that difficulty was still at the minimum limit of one, so the two versions did the same thing in practice.