While the answer by @rokenrock above might be true in some cases, it absolutely not to be taken for granted. For instance, there has been a changes in the way the engine handles models as recently as 4.25 or so - meaning that .uasset models authored with a newer version would simply not show up in a project create with an earlier version of the engine.
In short : while it is of course possible and totally fair to mark a an asset originally built with 4.2x as being compatible with 5.x (because it is), do not expect an asset made with 5.x to work with the previous generation of the engine.