What's the difference between ptát se and požádat? Both are translated as ask, as far as I can understand. Is ptát se usually used in terms of asking a question and požádat in terms of making a request?
You got it exactly right. Ptát se is to ask question. Požádat to NICELY ask/make request. They can kind of overlap in both languages at times.
I realize the lesson is teaching the use of abych here. But I'm trying by to understand the reason. Why would one say this instead of 'Kateřina mě požádala, na ni čekat'?
Your proposal does not make sense in Czech.
Good answer. Lol. I looked up a lesson on aby and think I have a better grasp of it now. Thank you, as always.