あなた I like to think is more like a "hey you" in english because you don't say that if you know the person's name. 君(きみ) Is used by people of a higher social status. Like a manager might call There worker 君. 君 is also used affectionitly in music and dramas. There is alot of ways to say you and I in Japenese than just あなた & 君. This girl explains It alot better than I can. But because There are so many ways to say you she has it split into 3parts. Part 1 https://m.youtube.com/?#/watch?v=2DqSfpmL2Ms Part 2 https://m.youtube.com/?#/watch?v=lJVBPODxzGQ Part 3 https://m.youtube.com/?#/watch?v=hGynRI8d6Zo I hope it helps.

in daily conversations, "あなた" and "きみ" is unnutural (formally) 役職(ヤクショク) > name >>>>> "あなた"=”きみ”>>>"おまえ">>>>>"てめえ"(rudely) for example 社長は今何をなさっていましたか? 太郎は今何やってる？ おまえは今何やってるの？ てめえは今何やってるんだよ？ see also https://www.youtube.com/watch?v=2a69uE4mw6g

I think あなた is better But both are fine

あなた is better. But if you don't know the person's name, you should ask him/her. Using the word あなた is not that rude but unnatural in converstaions. きみ is not natural at all in daily conversations and if the person is older than you, it sounds rude. きみ is used only in J-pop music haha

We basically do not say 'you' because it sounds weird. It depends on the phrase, though. But occasionally, we have to say 'you', then we would say 'あなた'.