Landing on the Moon with the software flown on Apollo 9.
This is a byproduct of the reconstruction of Sundance 306, the Apollo 9 Lunar Module software. Originally the AGC developers were just working on one set of LM software. In late 1967 they basically split development in two parts, one software for the lunar landing mission called Luminary and the other for Earth orbit manned test flights of the LM, called Sundance. I think the earlier version was already called Sundance, so Luminary was branched off from that. They had already worked a lot on the descent guidance code before the split, so Sundance already had landing code. They never did any more changes to it after the split I believe, so Sundance has the earliest AGC lunar landing code that we found so far. Only an earlier Sundance version would have something from earlier, but the earlier you get the less likely it is that it was already working.
But this version can definitely land! There are a bunch of bugs, some orbital parameter displays are broken in lunar orbit, some flags have to be set manually, but other than these obstacles, the Apollo 9 software would have been able to land on the Moon. And that code had just been left in there since more than a year before Apollo 9 flew.
I'll have at least one more video about Sundance, as there are some other interesting programs in there that were deleted from Luminary before any of the Luminary versions we have. It is onboard programs to calculate the lunar liftoff time for the LM, so the time of ignition to start the ascent to the CSM for rendezvous. During the actual moon landing this time was only calculated by mission control and given to the astronauts to write down.