This is a workflow that used to work but stopped working recently:
It turns out the questions were relevant questions and once we remove the relevancy, the the answers get pre-populated. I have an open Esri Support ticket and got an answer that this is an expected behavior. I read in documentation that you cannot pre-populate repeats (i.e. related questions) but I did not find any documentation/forums showing that relevant questions cannot get pre-populated. I wonder if someone in the community experienced similar issue.
Solved! Go to Solution.
I also got the same answer from the developer (via Esri Support) that "[...]If the question is not exposed when the survey is launched, you cannot pass an attribute via a custom URL."