I think version 4 will work with that key: http://www.diydatarecovery.nl/downloads/Demo/iRecover4Setup.exe
And .. We're not telling you can't use an older version, nothing wrong with that. But I think it isn't fair either to expect us to keep all older versions online. If your older version works, then sure, use it. But since you purchased that, we've put a lot of time and effort into making iRecover better, adding features, support for new file systems, larger disks etc.
In addition, when buying just about anything else, you are expected to take care of the purchased goods yourself (like, store them somewhere safe). There is no reason to think that this is different for a digital purchase.