Don't do it to yourself.
Some (most?) of models won't work for free credits. Which ones? No idea. The only way is attempting to generate an image and seeing 'This feature is unavailable with your current plan' or not. Pollo Image 1.6 is godawful. And when you attempt to delete stillborn disasters generated by aforementioned model you get another 'This feature is unavailable with your current plan' pop-ups. (Thankfully gend get deleted.) I managed to generate something serviceable with GPT-Image-1, but inability to make the gen private (unless you pay) made me delete it. Highly unrecommended unless you enjoy a sour taste in your mouth.