No anything you did in FIFA 20 on Ultimate team stays on that version. So you can load older versions and your squads will be as you left them. EA don’t turn off the servers for previous versions so you can still play online. FUT Champions is only available on the latest version however. When you start FIFA 21 Ultimate team it is new and starts from scratch. Coins from zero and only the random players you get as a new player (bronze, silver and couple of gold). You cannot transfer anything between versions. Although there is a one time FIFA points transfer if you had them on FIFA 20. With next gen consoles arriving during FIFA 21 progress continues onto the PS5 from PS4 and Xbox S/X from Xbox One. No need to buy FIFA again or start FUT again.