Differences between Server and 4GL Tool Versions

I am working on a product that uses Informix Dynamic Server 7.2.4, but is scheduled to upgrade to a more current release of the server. Is there someplace where I can get a comparison of the features for subsequent releases of Informix Dynamic Server (I know there are 7.3 and 9.2 releases and probably several in between). If somebody has any experience that would either strongly recommend or strongly discourage using a particular release, please advise. In addition, we are using version 6 of the 4GL development tool. I know there is a version 7 for this product. I am interested in similar information for this product. Finally, is there a product compatibility matrix for Informix products? Something that says which product/version combinations are compatible with other Informix product/version combinations? Thank you for your help. -Ira Rosen