The output is not in order, we can use a linked hashmap to resolve this but I am not sure if it is allowed.

create sequence diagrams while writing use cases

You can read on an example of the Decorator Design Pattern here: https://www.freecodecamp.org/news/the-basic-design-patterns-all-developers-need-to-know/

We should create use cases which will help us better design the UML.

IEEE SRS provides a description for each section of the SRS. Please make sure to read them first before writing our own software requirement specification.

What happens if the next iterations require us to remove the label assigned? Or change it? How are we going to prepare for that in terms of design?

Make unit tests for each individual unit in the source code

Fill the specific requirements section in the document along with the UML diagram since the UML diagram is about to be finished.