Hello @Julie
Welcome to ODK Community, when you get a chance, please Introduce yourself here!
To get labels of selected items (crops) in select_multiple you can use jr:choice-name() in combination with selected-at() since more items can be selected. The later function allows you to point to a desired index for label retrieval. However, I noticed your choices uses text labels, in which case selected-at() alone, might suffice to retrieve the label. I used the combo, should you use pseudo name (i.e.: numbers and short codes) in your choices.
As for controlling relevant based on number of selected items, you can use count-selected().
I made the changes in your HDDAP baseline - draft farmers questionnaire - test.xlsx, test it out and let me know if it worked for you.
Happy ODKing
Best,
Jules R