Re: No area "Exalted plains" available
Can you see it on the war table? You have to unlock it first with power points. The Exalted Plains is a location in Orlais. Here are all major locations (click for larger image):
If it's really not there, you could try the usual workarounds. The first is a power cycle of your PS4, which means turn it off, unplug it, wait for 30 seconds, then plug it back in and turn it on. You can also uninstall the game and then reinstall it. I don't think this affect saved games.
If none of that works, you probably hit a bug. I can't find any info on this, so it would be a very rare bug. To answer your second question: You can skip the Exalted Plains because it has no bearing on the game's plot line. It's exclusively for side content, but it's still a shame you miss out on it.
