Translation:The small blue car is moving in between those big buses.
It's not a beta/non-beta thing; it's to do with the fact that most courses use a text-to-speech (TTS) engine (a "computer voice"), but a few (e.g. Esperanto, Irish, Hungarian) have recordings of a real human speaker.
The computer voice can speak individual words as well as full sentences, and if a new sentence is created it can immediately have audio.
But live recordings don't record everything (there's a limit to the number of sentences that Duolingo pays for recording of), new sentences will not have audio, and there is only a single speed.
Between is accepted and in between isn't compulsory so that was a relief. Now, however, for a big question. Suppose I said A kicsi kék autó azok közé a nagy buszok közé halad. I think I'm now saying that the little blue car is moving into a position between those big buses. If I say között, the car is moving in between the buses and the buses are moving alongside the car so that relative positions remain largely unchanged. If I say közé, I'm saying that the car was not between the buses before moving but the movement brought the car to a position between those buses. Is that right?