With regard to a workflow for getting Unreal editor assets FBX mesh, Textures and Materials into previous engine 4 versions, you must have the newer and older versions editors installed on your system.
- Double Click on the project to open it, or any project you want to transfer to a lesser version engine.
- Navigate to the Mesh folder.
- Select the first mesh, then holding the shift key, select the last mesh. All meshes should now be selected.
- Right Click over any of the selected files and choose ‘Asset Actions’, then ‘Bulk Export’.
- Choose a Folder in the project of your earlier version engine, click ‘Select Folder’.
- In the FBX export window, click Export All.
- All the meshes and materials with textures will now be created in that selected folder.
- Open the project of the Older Editor.
- Open each material that has Masks and select Blend Mode as Masked (this setting doesn’t always export between shaders/materials), connect the A (alpha) channel of the Texture to the Opacity Mask node of the Material.
- Check other settings of the Materials.
That just leaves you to drag and drop the meshes into your scene. Make sure each mesh is set to Stationary before you build the Lighting, otherwise you may get errors.
I got this workflow transferring assets from 4.26 into 4.23
NOTE: I have not tried this method with Blueprints, Scripts etc.
I thought I would share this information as a working method of transferring mesh, texture and materials from one editor version to a previous version, which is not possible by simply opening a project in an earlier editor, unless you manually import everything but you will need access to the original fbx files using that method. You can do the reverse and open older projects into newer editors.