unreal 4.20.3 vs unreal 4.21.0

So I note epic games " Unreal " has made a new update but a user said that the old update before the new one is full of bugs? can anyone please check this is this is true or just made up, if this was the case that it’s full of bugs then how would I got about moving my project to the new update without having to remake the game?

You can copy and open your project with the newer version of Unreal and it will ask you if you want to convert to the newer version.

4.21 is still in preview releases, and not fully released.

All versions of UE4 have bugs, particularly the preview releases. But different bugs effect different people, it is impossible to say which version would be more bug free for your uses.