I'll try to answer your questions:
1. If it has been raining long enough, it should.
2. Let me explain you the temperatures. Warm and cool are minor temperatures and don't affect your sims too much. Hot and cold are moderate temperatures and affect sims outdoors. Freezing and heatwave are major temperatures and affect sims both indoors and outdoors.
3. Yes, it does. Confirmed by a SimGuru.
4. Windy walk is actually never done during the windy weather. It is done during the blizzard.
5. Question 5 doesn't exist. Let's go to 6.
6. I don't know actually. Maybe it does.
7. It sometimes appears after it's been raining for long.
8. Many players had that problem. It can happen.
9. Sometimes it does take more than one attempt.
10. Holiday decorations are actually banners and other things hung on the roof, foundations, fences etc. Yes, it is a good way to get free money.