if your using a photo, a locket is better because the image is visible and flat for viewing. mostly, you use a prayer box for little messages you can fold up

You can only use like locket if what you want to put into it is able to be folded pretty small for most of them. You can take a little piece of paper write a wish or prayer on it and fold it very small. It will then fit into the box. it is magnetic sealed. and the paper will usually stay in but if the paper is too large it will press against the sides and make it more likely to open up. My daughter really likes hers, pretty design on opposite side.

In terms of half-hard wire, half hard means that the wire is not flexible but can be bent.

I think you can.