Hm. Can't "those books" be an accusative in an elliptical English sentence? Wouldn't Şu kitapları be correct as well then?
An example "He reads those books" "What does he read?" "Those books". I suck at grammar but in German it would be an accusative and English being germanic yadda yadda yadda :-)
in a sentence where it is the object, yes (he reads those books: şu kitapları okur).
On its own as in here, or as the subject, no. Similarly you wouldn't translate "that dog" as "diesen Hund" to German without context, and the Duolingo course here also would only accept "dieser Hund" :)
Carla, yes. But the difference between them, is relative to the distance between the object and you. But have a look at this website: https://elon.io/learn-turkish/lesson/demonstratives, very clear table.