While there are other, very capable graphic editing applications, the Adobe applications are cross-platform (Windows and OSX). Furthermore, there are still very much the industry standard and proficiency in them is still assumed by prospective employers.
All the step by step activities are based around Photoshop and Illustrator and all assignment deliverables are requested in these file formats.
It's recommended that participants use the latest version of the applications.
The Rationale Document is an opportunity for participants to explain the design decisions taken. Participants provide insights regarding their design process, concept development, design evolutions etc.
It's a designer's role to make the case for design decisions to stakeholders within organisations/teams or to a client. In that role a designer must articulate why choices were made and avenues pursued without resorting to personal preference. Designers must argue about typeface or colour selections as being aligned with user needs or customer expectations.
Participants may amend the template provided or come up with their own but what is expected in the Rationale Document is insight into decisions made and information on the progression of the design from concept to final execution.