I did both types. The rewards one is simply pre-signing up for their rewards program if you are not already a member. It is just like a regular rewards program similar to fast food or Starbucks locations. And that rewards program is different from another rewards program those locations offer with their credit card holders. You do not need to apply for a credit card on the simple rewards program type. If they do not tell you about their credit card, you inquire if they happen to have a credit card and you gather the information and printed material they can provide. You have to practically pull teeth to get printed material as they will say everything is online, so just say: "Do you have the disclosure statement?" "I want to read the fine print on paper." The other one you act like you want to apply for the credit card and you start the application on their little terminal and get to the point where you are about to enter you SSN, but then you do not and make an excuse to do it later. On each you look around the store for signage advertising their rewards and/or credit card and note where you saw it inside the store. You need to catch a photograph of those signs, discreetly. The shop form is easy and covers these points listed above.
Actually, there really is no need for a certification, in my opinion. It is that easy. But as others have stated, I applied for another one and it sat there, so I withdrew my application. I did get paid for the ones I did, without any issues and a nice score, so I do not know what the hold out is. There are no age requirements or restrictions.