First, Great artwork.
I have no idea on the questions you asked, but for using the LTS version you just open it Blender 4.2 and then F4->append->double click the 4.4 blend file->Grease Pencil-> Then select the GP you want and click append. Opening directly does have a lot of issue. The only thing that I know of that doesn’t append is GP Geonodes. You will need to apply any GP geonode modifiers for it to append properly.
