So, why do you ask the same again?
You have the solution - really easy and built-in - for your questions.
There is the multiple question with the setting:
Then there is the single question with:
a. relevance equation (you don't need to check the "None" option. It is exclusive, so the count is only "1"
b. array filter
Then you get:
"None" is exclusive
Only one item selected
More than one item selected
And here the sample survey
Joffm
I chose "group by group" for better display. If you want to display "question by question", feel free to do so.