You just need to keep the discs,not the console. if it's not retro-compatible then you aren't going to be able to play on the console because of architecte differenczs.
But the PS5 can play PS4 games, early PS3 could play PS2 games and so on. And Xbox is entirely retro-compatible because they used the same architecture.
But the PS5 can play PS4 games, early PS3 could play PS2 games and so on. And Xbox is entirely retro-compatible because they used the same architecture.