Backend:

Product Name-T-shirt-Red

Admin setting should be in backend in product page design section:

Product> Tshirt Red > Design Tab> No Layout update 

Frontend:

The product Page screen look like this:

Note: This submitting question will work when the user is registered

After submitting Question screen show message like this:

In admin its look like this:

When Admin answer question and show on the product page:

The status should be Yes and need to put the answer. 

Note: If the admin doesn’t want to answer this question, that’s also dependent on the admin user if he wants to answer and approve the question. 

After the Admin answers the question, the user receives the email with a question and answer.