A - Yes, correct. B - "I don't know. Whatever it is, it can't be good."

When I hand something to someone when they have been waiting for it or asked for it. For example, a kid asked me to get something on the top shelf for him. I get it and hand it to him and can say, "here you go." Or if I am helping someone ride a bike, I push him away and he starts peddling away from me, I can say, "haha, there you go!" "Here you are/There you are" can be used when I just found somebody, perhaps they were hiding. These aren't strictly what they are used for, but such examples.

It means what manufacturer it is -- for example I ask what make your car is. You can say BMW or Audi.

All correct! Last one would be "There hasn't been a day that I haven't missed you."

밥 먹으러 갈래? Want to go eat? 밥 먹으러 갈자! Let's go eat!

Perfect :)

This winter was the coldest one we'd ever spent. This summer was the hottest one we'd ever spent.

Verb stem + 지 않아요 = can not "verb" So 보이지 않아요 means "can't see"