Making a skin is only making a .jpg. If you want to view them on the car then obviously the answer is no, photoshop doesn't do that, the CMX viewer [main site other/other downloads] does.
PS4 will have less features than the newer versions (duh :P) and as such some psd templates may not work, or work properly, but in general, yes you CAN indeed skin with it
Hmmm kinda right & kinda wrong... plain layered bitmap based PSD files are usually backwards compatible so you're kinda wrong although the compression methods they use have changed over time so you're kinda right