You see, there is still this last comma before the "))))))))...".
Remove it

If I put a value at the end of the expression it seem functioning:
,if(week==19,substr(QDef_19,0,46),0))))))))))))))))))))}
didn't understand why but I'm pragmatic ...
 

I declared victory too soon !!! If I hide the question records was saved blank !!!

I breakdown!!

Hi, 
I never tested in your stone age version.
Somewhere I have a 2.06.
Let's see.
And I missed that in this version it probably was not allowed to omit the FALSE part in an IF.

On the other side: What for do you want to have this text? It's only a bit more comfortable.
But in your export of the data you have everything you need:
The week and the code of the selected answer.
 

You should use better codes than "SQ001", "SQ002" (which seem to be relicts from your initial "multiple" question here) like 1,2,3,4,... 

Okay, tested in 2.06.
 

Everything works fine,too. Except that you can't hide the question be "Always hide this question."
So, either hide it by javascript.
Or show it as a kind of confirmation with a text like "You selected abc"
 
Joffm