I think that "you can repeat IT whenever you want" should be an accepted answer because although there's no "det" in the Swedish sentence, the sentence without the "it" i.e. "you can repeat whenever you want" doesn't really mean anything in English.
The only thing that it can mean is "you can repeat the current year of school whenever you want" but even this doesn't really make sense because you can't do that whenever you want!
Since 'rehearse' is a correct option, shouldn't 'practise' (or 'practice' since Duo is American) be possible as well?
1) In English two words exist - each having a different emphasis. The same can be true in Swedish.
2) Practising is not the same as rehearsing in my opinion
De betyder samma sak (to repeat), men "repetera" kan också betyder "to rehearse".
Because "practice" (öva eller träna) is more to become better at something, while "repetera" simply means you are rehearsing or repeating something. They are similar but have different meanings.
I wrote "You can repeat when you want" and my answer was marked wrong. Thus, in English "when" refers only to a specific point in time, whereas "när" (like "quando" in Italian) can mean both "when"" and "whenever", right?
Hm, are you sure it said it was wrong? Because it was entered with a double space typo in the system (I've fixed that), but it should have been accepted anyway.
Ja, det är jag (jag är säker). Så var mitt svar korrekt, eller hur? :-)