Not if you are documenting your requirements analysis. The design is generated from the requirements analysis. Moreover, you can view the complete call dependency diagram and context diagram for each method and data for its usage. On the contrary, you will be speeding up your development process since the discovery time is significantly reduced.

Less than half an hour is needed to get started. Few simple steps are involved.

Yes, you can use to define any functionality of the application and then incorporate in the application. This way, you can gradually define the application.

You can discontinue at any stage of the development process without any loss or harm, you will be having the complete source code with documentation. It is not invasive.

OODUSA is objective, explicit.

Visitor pattern and in case of distributed systems, Singleton pattern.

Yes. Use OODUSA as a precursor to OOAD. Most of the problems arising in OOAD development are due to runtime dependencies so if you do the dependency analysis and get navigation tree first then these problems will not arise. The method code is invariant, what is changing is the method grouping.