It is not the least bit feasible. Three VC as turn 500 starts is theoretically possible, but the Time Victory would have to be coordinated with CV and WL vote. The WL vote would be very difficult to sync up. I am not sure if that is even mathematically possible. In any case, the player would only get one VC screen.
You would only get one victory screen, but I think the question implies getting every single victory type on the same turn, even if only one is counted by the game officially. Save up your last spaceship part for when you can take the last capital on a world leader vote turn, and pop a great musician in an enemy city to get enough tourism to overtake everyone culturally. That's definitely possible and that's four victories on one turn right there.
Synching it up to do all of this on turn 500 is difficult though, because the question implies you are winning that turn, which means you're successfully stopping everyone else from launching a spaceship while simultaneously not getting an accidental cultural victory, and at the same time coordinating your discovery of printing press (and maybe discovery of other techs) to specific turns to get a world leader vote on that turn. Five 'victories' on one turn might be possible, but I don't think I could pull it off. Four (aka all but the time victory) would take a bit of effort, but wouldn't be too hard to get.
Synching the diplo victory vote would be an annoying but not a particularly interesting challenge. Preventing your opponents from winning a science victory while avoiding an accidental cultural victory, but at the same time setting yourself up for a turn 500 cultural win is a much more interesting challenge. To do that, you would probably want a strong domination strategy, and then to identify the cultural powerhouse, and make that the last civ left to conquer. I think you would want to place spies in all of their cities to watch for spaceship parts, and go selectively all out with nuclear missiles. Take away their uranium (nuke or pillage their uranium if you can to avoid being nuked), and nuke their capital to ashes. Keep their other cities alive to the best of your ability because you need them to generate culture. Maybe even let them have a couple of cultural city state allies if possible. Try to have a city nearby their empire with stealth bombers to destroy any and all spaceship parts heading towards their capital, and nuke those parts if you need to. Their nuked capital shouldn't be able to make spaceship parts, and as a side bonus, should disconnect any railroads and give you time to destroy their space pieces that are heading to the capital.
I imagine that's how I'd try to do it, but it wouldn't be easy.
