unable to select items in Preview

Unlike a PDF file, when you apply an annotation to an image file, and the file is saved (or autosaved), you lose any future opportunity to select those annotations as they are now burned into the image.

You need a vector graphics tool that supports layers so you can open the original image as a base layer, and then add additional content in layers above it. The free GIMP (GNU Image Manipulation Program) would allow you to do this. There are a bunch of free, online, or fee applications to choose from so, pay attention to the details that best suit your workflow needs.

Otherwise, look in the Mac App Store, and search for image editor. Read the small print for any application with the most star-rating that looks like its free, as it may be a trial with subscription requirement. Also, scroll down in these and click on the Compatibilty link to see what operating system it requires.