Why is it important to be able to model a system using UML or to describe

Q1)  Why is it important to be able to model a system using UML or to describe it in pseudocode? How would this work benefit you when you move on to write actual code? How do the processes and final intent in writing pseudocode and modeling UML diagrams differ? 

Q2) What are some tools you can use to write pseudocode and UML diagrams? Give at least one example of each and describe why you chose them. 

Q3)  This schema is used in data warehouse models where one centralized fact table references the number of dimension tables so as the keys (primary key) from all the dimension tables flow into the fact table (as a foreign key) where measures are stored. This entity-relationship diagram looks like a star, hence the name.  Star schema is probably the most popular schema in dimensional modeling because of its simplicity and flexibility. What are some of the other benefits of using the Star Schema?