Probably Densglass. Exterior sheathing part of the one-hour (or two hour) requirements for fire resistivity.
Wood frame buildings can go to 4 or 5 stories depending on where you are building.
Yes. Guess that would be covered with a stucco material eventually.
These buildings look to be about 12 stories.
Much higher than that. Article in Popular Science, March 2014 about wood skyscrapers. Swedish authorities gave the go-ahead for building a 34-story wood tower in Stockholm. A 30-story wood tower is to be built in Vancouver. Chicago wants to build a 42-story wood tower. The new technology says it's actually safer than a steel framed building.