(SG)How can I obtain a PS4 copy of FFXIV:ARR?

[Niwashi]

I'm in the US, so don't have direct experience with trying to register though an EU account, but going by how it's listed on the box, I don't think it matters for PS4. I got the boxed versions for both PS3 and PS4. The box for the PS3 version labels the region as "1", but the box for PS4 labels the region as "ALL". I don't think there is such a thing as a Region 1 PS4 copy.

(In fact, every PS4 game I have lists "ALL" for the region, and I remember hearing back when PS4 was first coming out that it doesn't really do regions like earlier console generations do. I don't remember where I heard that, so can't vouch for certain whether that was solid info or a rumor, but seeing "ALL" listed on all the games seems to support it.)

I figured I should give it a try, but ended up I couldn't register the code since the registration key format was different.

Where did you try to register it? With the PC version being registered through Mog Station, I've heard other people going from PC to PS3/4 trying to go there for the console versions as well, which won't work. PS3 and PS4 versions are registered on the console itself, through Sony's PlayStation Store. (Go to the PlayStation Store from your PS4 console, and select "Redeem Codes".)

I have also tried to buy the game off PS Store but was not able to. The site would require me to log in, then redirect me to the SGD-EN site which says the site is invalid.

I'm not sure what you mean by "site" since it's not something you do on the web. (It requires an internet connection of course, and you have to be logged into the PlayStation Network, but it's from the built in software of the console and no browser involved, so it's not like a website.) Go on your PS4 and enter the PlayStation Store from there.

I don't see any links that allows me to get the digital download for PS4. Only offers PC download or physical copy for PS4.

That's because console downloads have to be done on the console. You can't download console versions from a website because you can't download them on a computer.