its ok to start with 4 if you want, it will be easy to move your stuff to 5.
5 is essentially an upgraded version of 4 and most features still apply.
its not as drastic of a change like 4 was from 3 so you can port from 4 to 5 just fine. wish there was an option to change the Ui since they changed it between engines, cmon’ EG give us some ui customization!
also use blender , its a great freeware 3d tool that complements any 3d game engine.