Formaldehyde does not have an R Group. There are other aldehydes that are available right now that will come with an R Group. What makes formaldehyde different is that it comes with a hydrogen atom instead. Another type of difference that you can sense from these two is the types of odor that they can produce.
You may notice that formaldehyde comes with a pungent odor while aldehyde comes with a more pleasant odor. Another difference that you will notice is that they will come in different states. You can expect that formaldehyde is always going to be in a gaseous state while the aldehyde may come in a gaseous or liquid state.