Your question did not specify preschool, elementary school, junior high, or high school.
1. Almost no preschools have uniforms. Most elementary schools don't have uniforms, a small percentage do. Most junior high and high schools have uniforms, a small percentage don't.
2. Yeah, for the schools that do have uniforms, it gets cold, there are usually provisions for that (such as allowing long stockings, jersey pants, etc)
3. Usually, yes. Not always, though. For subjects like PE, home ec, art, and science, the students often go to a different room. And the numbering doesn't always go 1A, 1B, etc; sometimes it's 1-1, 1-2, 1-3, like that.
In some schools the class actually gets a name, like the name of a fruit or flower (it's not real common, but it happens in preschool and elementary schools sometimes).
4. Depends on the school. Some schools have different committees for different things, and the committee member that's specifically for the lifestyle events like the school festival would handle that. Most preschools, elementary schools and junior high schools don't have that kind of school festival, though.
5. Usually, yes, and the students (or their parents) pay a little each month, even for public schools, to fund the trip. They often have a scholarship fund for kids who can't afford it, too. (Preschools don't have these school trips, but elementary schools on up usually do.)