If you want to refer to an an answer from a previous question you can use the question name to use the answer as a variable. See: https://docs.getodk.org/form-logic/#variables
Here is an example of one list of options, that is filtered for a second question based on what was selected in the first.
filter-example.xlsx (12.8 KB)
Here is an example of a repeat group that repeats for each answer from a select_multiple.
repeat-loop.xlsx (16.8 KB)
Also, I noticed you tagged your post with odk-aggregate. If you are using Aggregate, please note that it has reached end-of-life and is no longer being updated or supported. Consider switching to Central because it's actively developed.