Hello,

in this scenario you do not need any javascript. In this case it is nonsense.

Remember: This thread is about filtering single -> single. (single has no subquestion relevance)

Just use subquestion relevance in Q2 and array filter in Q3.
Q2:

Q3:



well, it's German, but you see.
And I changed these IMHO silly "lettercodes (A1, C3)" to numerical codes.

And remember: To use "array filter" the codes of Q2 and Q3 have to be exactly equal.

See example:


Best regards
Joffm

And, the best is to read the manual about question types and about "Adding answers and subquestions"