Snapchat help me? (Handy, Social Media)

I’ve had Snapchat since yesterday and have a few questions about it, as some things are still undecided for me. I hope someone can answer that.

1. What do these emojis mean (hang in the picture)?

2. When do you get flames with someone?

3. Why are the notification / message red / blue / purple? (Picture 2)

4. What does this number stand for? (Picture 3)

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