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This should help answer some of your questions : https://www.curvediscussion.com/certifiablytableau-tableau-desktop-specialist/
Basically the exam runs on a virtual machine, you don't have to create the same viz - just get the answer to the question.
Recommend you check out the Exam Guide from Tableau and how to prep the Exam Set-Up, it has all the information you need. The blog Chris McClellan mentioned has a lot of great info too and if interested there's a Test Exam on learningtableau.com you can take in preparation.
See links below ... good luck!
Tableau Exam Guide for Desktop Specialist Exam
Tableau Specialist Exam 1 (Beta)