I guess that would be wrong, because you specify "particular"(these) apples. Here its asking in a general sense, not a specific case of apples.
When you see the umlaut letters under the translation box, there's also a Shift button - click on that and then it shows you the umlaut letters in capitals, so you click the one you need.
How would you say "Would you like apples?" (i.e. you are offering someone apples)
you can use another verb: "Möchten". as in "Möchtest du Äpfel?" that's what more in use in daily routine (to my experience).
While this sentence is clearly "Do you like apples?" because Äpfel is plural, is there a German equivalent of the English "Do you like apple?", using apple as a non-countable noun? In english that's typically used for apple that has been processed in some way - cooked, or mashed, or similar.
No, it's still usually "apples" unless you use apple as an adjective, like "apple pie" or "apple filling" but if it's just in reference to the apples themselves, it's apples
Are there conversationally understood words, like in English I would just ask someone "You like apples?" (which is what I tried, counted wrong) because the "do" is understood as part of the question. Or is this just trying to teach proper grammar as well?