That's only a sentence fragment. "Although" implies there's something else coming after the initial phrase. For example: "Although bravery is not confined to the army, it's hard to find it elsewhere." As it stands, it means that bravery doesn't exist only in the army, but you need the rest of the sentence to know exactly what it means.

I meant: "Would it be okay to use an actual Japanese name instead of my English name?" Sorry!

It sounds like this is a part of a larger body of text. Out of context, I'm not sure what it means. You provide the paragraphs/context for these sentences?

That sentence doesn't make much sense. I'm not exactly sure what you mean, could you explain a bit more? Maybe you mean to say "I need to study hard." ?

I think they mean about the same thing. Would you give an examples of use in a sentence?

As a prefix, it's usually pronounced: ee-koe.

You could say: "It's an unbranded T-shirt." Technically you could probably say: "It's a non-branded T-shirt." However, this doesn't sound very natural.