They are actually impossible, you can't even click that fast. You are supposed to buy the extender or whatever.

The initial ones are manageable but not if you have to listen to how each word is pronounced. I'm not sure what the maximum level is but I think you're right that it's impossible to solve all of them without the time extender.

You have to know the words well enough that you don't need to listen and just read directly.

FWIW I just got max level (it's a non-Latin language so the initial exercises are all repetitions of recognizing certain glyphs and their combinations) and it turns out that there's nothing special about it except you get to repeat it instead of moving on to a higher difficulty. So "it's actually not possible to beat it" is probably more of a calibration issue than a blatant money grab. The only reward is more XP.