Hi,
I have no personal experience of this, but if you are the same publisher, I am pretty sure you can release the same game for different platforms, as long as the app id is unique. But it's always best to only have one app, with internal switch to enabled disable what's required for that platform.
Resolution issue depends on content, for UI, if you use a third part you will have access to tools to deal with it, else, you will need to either create two different scene and content one for non retina and one for retina or go more clever and switch graphics on the fly, but that's only one part of the problem, you then have to deal with aspect ratios...
Bye,
Jean