1. I send messages to my friends on Kakao Talk.

Question

2. I text to my friends on Kakao Talk.
3. I send messages in group chatting rooms on Kakao Talk.
4. I chat with friends in group chats on Kakao Talk.
[Which ones are correct? Would you correct errors?]

5. I will perform in a dance contest next month.
6. I will perform at a dance contest next month.
[Which preposition can we use, in or at? Can we use both?]

7. I will perform at a school festival next month.
8. I will perform in a school festival next month.
[#7 is right. #8 is wrong. How come #8 is wrong?]

Answer 1

I think all of these sentences are correct. We would say a "chat room" instead of "chatting room", but calling it a chatting room is grammatically correct, if not common usage. You may use "at" or "in" in these situations. #8 is not wrong. To say you will perform in a contest or festival means you are a participant in the event. To say you will perform at the event mean you will entertain that event participants, so it depends on what you mean, in or at. Both are correct, but mean something slightly different.

Answer 2

PS -- In 2, I would omit the word "to" -- it's not incorrect, but in today's normal usage (unfortunately), the preposition is usually left out!