LR 4 & PS 5 compatible?

Question

Is LR 4 compatible with PS 5?  That is if I switch from LR3 to LR 4, will I still be able to export to PS 5, edit the files in PS 5 and come back to LR for printing?

Answer 1

Yes you will (I assume you mean CS5). If you ensure your PS has the latest available version of Adobe Camera Raw installed, you will get partial compatibility by the direct route, meaning that LR passes the image and the settings to ACR which renders a converted file for PS to edit. However as LR moves through its 4.x versions it is slowly "drifting out of reach" of  CS5 and now only CS6 (with its newer ACR 7.x) is completely compatible by this method.
You do, however have a "Render in Lightroom" alternative which works by passing an already-converted file to the other program for editing. This does not rely on any ACR whatsoever, and can be used with more or less any image editing program, from Adobe or not, old or new. Because this way LR carries out the conversion, the TIFF (or PSD) involved reflects every detail of your LR adjustments accurately.
Whichever of the above methods has happened, LR4 works with CS5 exactly the same as LR3 does, thereafter - you can use the Edit Original method to go back and do some more PS editing of the same file. LR tracks these external changes, overlays any new further adjustments of its own, and outputs / prints / etc as normal.