I haven't found a topic for this but if there is: I am sorry.
My question is not about the "normal" Katakana. I'm doing okay with that. But there are some new additions like ヴィ or クォ
I have a book where some of those additions are listed but not all. Also some are listed that I can't write with my PC like ズィ. And there are some that are listed elsewhere (Wiki has a list of all of them).
My question is: which combinations are official and therefore I can use? Or are those combinations just as one likes? For example I have seen デュ used as ju and as dyu. is that wrong/outdated to use デュ as du (since you normally use ジュ) and it should be normally be dyu or what is going on?
As you can see I am very confused. I want to know what I should learn.