Short answer, you don't need to know too much to begin.
Longer answer, you need to know a lot to be great.
This is similar to guitar students of mine who all want to play the latest songs now but they don't know how to use their fingers to hold individual notes let alone chords - they set themselves up for failure by insisting on achieving what is really 3-6 months down the track from their first lesson.
We eventually get to a point where they understand why it was impossible to teach them what they wanted to know on day one, if they stick at it. They reach this point on their own because they can suddenly play a whole lot of things they couldn't before, all down to practice and patience.
The same thing with piano or any other instrument really - you need to learn the mechanical aspects of holding your hands and producing the sound in a controlled manner - that takes time and patience. Learning chords, learning scales, learning arpeggios are all part of the learning the mechanics.
You are describing a situation where you are being asked to memorise facts. To memorise facts you have to review them and apply them until you are no longer thinking about how or why or what but just do. Go to
teoría - Music Theory Web and use their ear training and theory training software to assist you with memorising these facts. 10 minutes each day will cement these for the rest of your life (well at least until you develop severe Alzheimers or oldtimers memory problems).
Taking pumpthrusts points above I was in category 3 when I started at university and most of the theory work was a romp because I wasn't thinking about it but just doing it. I had to work at hard at mastering rhythmic dictation but that was because it was something lacking in my early education, a lack that I eventually overcame. I insist on rhythmic work as the foundation of all of my teaching with private students as everything can be reduced to timing in the end (any pitch/freq is simply a very fast rhythm at heart (repeated pulses)) - the better your rhythmic understanding the better your performances.